TestLegacyTSOServer is flaky

## Bug Report

I create a [PR](https://github.com/tikv/pd/pull/8598) without any code changes, but the integration CI job "PD Test / chunks (8, TSO Integration Test) (pull_request) " failed:

```log
[remote-peer-cluster-id=92a8a50d4bd1be75] [local-member-id=90978eff05ad95e7] [local-member-cluster-id=fa7dba492a46a30c] [error="cluster ID mismatch"]
server_test.go:78:
Error Trace: /home/runner/work/pd/pd/tests/integrations/tso/server_test.go:78
/home/runner/go/pkg/mod/github.com/stretchr/testify@v1.8.4/suite/suite.go:154
/home/runner/work/pd/pd/tests/integrations/tso/server_test.go:55
Error: Received unexpected error:
Etcd cluster ID mismatch, expect 18049787704975467[276](https://github.com/tikv/pd/actions/runs/10734113227/job/29768683433?pr=8598#step:4:277), got 10567878002150063733
github.com/tikv/pd/pkg/utils/etcdutil.CheckClusterID
/home/runner/work/pd/pd/pkg/utils/etcdutil/etcdutil.go:102
github.com/tikv/pd/server.(*Server).startEtcd
/home/runner/work/pd/pd/server/server.go:343
github.com/tikv/pd/server.(*Server).Run
/home/runner/work/pd/pd/server/server.go:619
github.com/tikv/pd/tests.(*TestServer).Run
/home/runner/work/pd/pd/tests/cluster.go:127
github.com/tikv/pd/tests.RunServer.func1
/home/runner/work/pd/pd/tests/cluster.go:577
runtime.goexit
/opt/hostedtoolcache/go/1.21.13/x64/src/runtime/asm_amd64.s:1650
github.com/tikv/pd/tests.RunServers
/home/runner/work/pd/pd/tests/cluster.go:589
github.com/tikv/pd/tests.(*TestCluster).RunInitialServers
/home/runner/work/pd/pd/tests/cluster.go:601
github.com/tikv/pd/tests/integrations/tso.(*tsoServerTestSuite).SetupSuite
/home/runner/work/pd/pd/tests/integrations/tso/server_test.go:77
github.com/stretchr/testify/suite.Run
/home/runner/go/pkg/mod/github.com/stretchr/testify@v1.8.4/suite/suite.go:154
github.com/tikv/pd/tests/integrations/tso.TestLegacyTSOServer
/home/runner/work/pd/pd/tests/integrations/tso/server_test.go:55
testing.tRunner
/opt/hostedtoolcache/go/1.21.13/x64/src/testing/testing.go:1595
runtime.goexit
/opt/hostedtoolcache/go/1.21.13/x64/src/runtime/asm_amd64.s:1650
Test: TestLegacyTSOServer
--- FAIL: TestLegacyTSOServer (2.25s)
FAIL
```

- Run record: https://github.com/tikv/pd/actions/runs/10734113227/attempts/1?pr=8598