lightning import failed when inject pd leader network partition or io delay with error "tidb lightning encountered error: rpc error: code = Unavailable desc = not leader"

## Bug Report

Please answer these questions before submitting your issue. Thanks!

### 1. Minimal reproduce step (Required)
1、run lightning
2、inject pd leader network partition

### 2. What did you expect to see? (Required)
lightning can success

### 3. What did you see instead (Required)
Run Lightning failed.
cmd start at 2024-01-27 03:55:51
cmd failed at 2024-01-27 04:05:20
stdout:
Verbose debug logs will be written to /tmp/lightning.log.2024-01-26T19.55.51Z

+----+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+
| # | CHECK ITEM | TYPE | PASSED |
+----+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+
| 1 | Source csv files size is proper | performance | true |
+----+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+
| 2 | the checkpoints are valid | critical | true |
+----+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+
| 3 | table schemas are valid | critical | true |
+----+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+
| 4 | all importing tables on the target are empty | critical | true |
+----+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+
| 5 | Cluster version check passed | critical | true |
+----+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+
| 6 | Lightning has the correct storage permission | critical | true |
+----+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+
| 7 | local disk resources are rich, estimate sorted data size 78.16GiB, local available is 3.399TiB | critical | true |
+----+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+
| 8 | Cluster available is rich, available is 5.315TiB, we need 234.5GiB | performance | true |
+----+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+
| 9 | TiKV stores (1, 4, 5, 6) contains more than 1000 empty regions respectively, which will greatly affect the import speed and succes | performance | false |
| | s rate | | |
+----+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+
| 10 | Cluster region distribution is balanced | critical | true |
+----+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+
| 11 | no CDC or PiTR task found | critical | true |
+----+------------------------------------------------------------------------------------------------------------------------------------+-------------+--------+

{"level":"warn","ts":"2024-01-26T19:56:57.392Z","logger":"etcd-client","caller":"v3@v3.5.2/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"etcd-endpoints://0xc000cbfc00/tc-pd:2379","attempt":0,"error":"rpc error: code = DeadlineExceeded desc = context deadline exceeded"}
{"level":"warn","ts":"2024-01-26T19:57:19.737Z","logger":"etcd-client","caller":"v3@v3.5.2/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"etcd-endpoints://0xc000cada40/tc-pd-2.tc-pd-peer.ha-test-lightning-tps-6330128-1-657.svc:2379","attempt":0,"error":"rpc error: code = DeadlineExceeded desc = context deadline exceeded"}
{"level":"warn","ts":"2024-01-26T19:57:23.419Z","logger":"etcd-client","caller":"v3@v3.5.2/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"etcd-endpoints://0xc000cbfc00/tc-pd:2379","attempt":0,"error":"rpc error: code = DeadlineExceeded desc = context deadline exceeded"}
{"level":"warn","ts":"2024-01-26T19:57:29.423Z","logger":"etcd-client","caller":"v3@v3.5.2/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"etcd-endpoints://0xc000cbfc00/tc-pd:2379","attempt":0,"error":"rpc error: code = Unknown desc = context deadline exceeded"}
{"level":"warn","ts":"2024-01-26T19:57:45.742Z","logger":"etcd-client","caller":"v3@v3.5.2/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"etcd-endpoints://0xc000cada40/tc-pd-2.tc-pd-peer.ha-test-lightning-tps-6330128-1-657.svc:2379","attempt":0,"error":"rpc error: code = DeadlineExceeded desc = context deadline exceeded"}
{"level":"warn","ts":"2024-01-26T20:00:57.340Z","logger":"etcd-client","caller":"v3@v3.5.2/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"etcd-endpoints://0xc000cbfc00/tc-pd:2379","attempt":0,"error":"rpc error: code = DeadlineExceeded desc = context deadline exceeded"}
{"level":"warn","ts":"2024-01-26T20:01:21.793Z","logger":"etcd-client","caller":"v3@v3.5.2/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"etcd-endpoints://0xc000cada40/tc-pd-2.tc-pd-peer.ha-test-lightning-tps-6330128-1-657.svc:2379","attempt":0,"error":"rpc error: code = DeadlineExceeded desc = context deadline exceeded"}
{"level":"warn","ts":"2024-01-26T20:01:23.345Z","logger":"etcd-client","caller":"v3@v3.5.2/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"etcd-endpoints://0xc000cbfc00/tc-pd:2379","attempt":0,"error":"rpc error: code = DeadlineExceeded desc = context deadline exceeded"}
{"level":"warn","ts":"2024-01-26T20:01:29.346Z","logger":"etcd-client","caller":"v3@v3.5.2/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"etcd-endpoints://0xc000cbfc00/tc-pd:2379","attempt":0,"error":"rpc error: code = DeadlineExceeded desc = context deadline exceeded"}
{"level":"warn","ts":"2024-01-26T20:01:37.796Z","logger":"etcd-client","caller":"v3@v3.5.2/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"etcd-endpoints://0xc000cada40/tc-pd-2.tc-pd-peer.ha-test-lightning-tps-6330128-1-657.svc:2379","attempt":0,"error":"rpc error: code = DeadlineExceeded desc = context deadline exceeded"}
{"level":"warn","ts":"2024-01-26T20:05:03.832Z","logger":"etcd-client","caller":"v3@v3.5.2/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"etcd-endpoints://0xc000cada40/tc-pd-2.tc-pd-peer.ha-test-lightning-tps-6330128-1-657.svc:2379","attempt":0,"error":"rpc error: code = DeadlineExceeded desc = context deadline exceeded"}
{"level":"warn","ts":"2024-01-26T20:05:10.420Z","logger":"etcd-client","caller":"v3@v3.5.2/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"etcd-endpoints://0xc000cbfc00/tc-pd:2379","attempt":0,"error":"rpc error: code = DeadlineExceeded desc = context deadline exceeded"}
tidb lightning encountered error: rpc error: code = Unavailable desc = not leader

error is from here:
rpc error: code = Unavailable desc = not leader
[github.com/tikv/pd/client.(*client).respForErr](http://github.com/tikv/pd/client.(*client).respForErr)
/go/pkg/mod/[github.com/tikv/pd/client@v0.0.0-20230904040343-947701a32c05/client.go:1942](http://github.com/tikv/pd/client@v0.0.0-20230904040343-947701a32c05/client.go:1942)
[github.com/tikv/pd/client.(*client).UpdateServiceGCSafePoint](http://github.com/tikv/pd/client.(*client).UpdateServiceGCSafePoint)
/go/pkg/mod/[github.com/tikv/pd/client@v0.0.0-20230904040343-947701a32c05/client.go:1664](http://github.com/tikv/pd/client@v0.0.0-20230904040343-947701a32c05/client.go:1664)
[github.com/pingcap/tidb/br/pkg/lightning/restore.(*gcTTLManager).doUpdateGCTTL](http://github.com/pingcap/tidb/br/pkg/lightning/restore.(*gcTTLManager).doUpdateGCTTL)
/home/jenkins/agent/workspace/build-common/go/src/[github.com/pingcap/br/br/pkg/lightning/restore/checksum.go:455](http://github.com/pingcap/br/br/pkg/lightning/restore/checksum.go:455)
[github.com/pingcap/tidb/br/pkg/lightning/restore.(*gcTTLManager).addOneJob](http://github.com/pingcap/tidb/br/pkg/lightning/restore.(*gcTTLManager).addOneJob)
/home/jenkins/agent/workspace/build-common/go/src/[github.com/pingcap/br/br/pkg/lightning/restore/checksum.go:411](http://github.com/pingcap/br/br/pkg/lightning/restore/checksum.go:411)
[github.com/pingcap/tidb/br/pkg/lightning/restore.(*tikvChecksumManager).Checksum](http://github.com/pingcap/tidb/br/pkg/lightning/restore.(*tikvChecksumManager).Checksum)
/home/jenkins/agent/workspace/build-common/go/src/[github.com/pingcap/br/br/pkg/lightning/restore/checksum.go:341](http://github.com/pingcap/br/br/pkg/lightning/restore/checksum.go:341)
[github.com/pingcap/tidb/br/pkg/lightning/restore.DoChecksum](http://github.com/pingcap/tidb/br/pkg/lightning/restore.DoChecksum)
/home/jenkins/agent/workspace/build-common/go/src/[github.com/pingcap/br/br/pkg/lightning/restore/checksum.go:161](http://github.com/pingcap/br/br/pkg/lightning/restore/checksum.go:161)
[github.com/pingcap/tidb/br/pkg/lightning/restore.(*TableRestore).postProcess](http://github.com/pingcap/tidb/br/pkg/lightning/restore.(*TableRestore).postProcess)
/home/jenkins/agent/workspace/build-common/go/src/[github.com/pingcap/br/br/pkg/lightning/restore/table_restore.go:874](http://github.com/pingcap/br/br/pkg/lightning/restore/table_restore.go:874)
[github.com/pingcap/tidb/br/pkg/lightning/restore.(*Controller).restoreTables.func7.1](http://github.com/pingcap/tidb/br/pkg/lightning/restore.(*Controller).restoreTables.func7.1)
/home/jenkins/agent/workspace/build-common/go/src/[github.com/pingcap/br/br/pkg/lightning/restore/restore.go:1695](http://github.com/pingcap/br/br/pkg/lightning/restore/restore.go:1695)
runtime.goexit
/usr/local/go/src/runtime/asm_amd64.s:1594

### 4. What is your TiDB version? (Required)
./tidb-server -V
Release Version: v6.5.8
Edition: Community
Git Commit Hash: 44f39e98a29e19bc00f2d6c1a7ab1609a7a9e822
Git Branch: heads/refs/tags/v6.5.8
UTC Build Time: 2024-01-26 04:29:55
GoVersion: go1.19.13
Race Enabled: false
TiKV Min Version: 6.2.0-alpha
Check Table Before Drop: false
Store: unistore
2024-01-26T19:59:32.387+0800