TestRandomShutdown is unstable

## Flaky Test

TestMicroserviceTSOClient/TestRandomShutdown

### Which jobs are failing
```bash
2024-04-19T09:02:55.0852245Z [2024/04/19 09:02:55.084 +00:00] [WARN] [grpclog.go:46] ["[core][Channel #163 SubChannel #166] grpc: addrConn.createTransport failed to connect to {Addr: \"127.0.0.1:34669\", ServerName: \"127.0.0.1:34669\", }. Err: connection error: desc = \"transport: Error while dialing: dial tcp 127.0.0.1:34669: connect: connection refused\""]
2024-04-19T09:02:56.2446819Z === RUN TestMicroserviceTSOClient/TestRandomShutdown
2024-04-19T09:02:56.2494552Z testutil.go:83:
2024-04-19T09:02:56.2496270Z Error Trace: /home/runner/work/pd/pd/tests/integrations/mcs/testutil.go:83
2024-04-19T09:02:56.2498557Z /opt/hostedtoolcache/go/1.21.9/x64/src/runtime/asm_amd64.s:1650
2024-04-19T09:02:56.2500053Z Error: "449188299075223585" is not less than "0"
2024-04-19T09:02:56.2501353Z Test: TestMicroserviceTSOClient/TestRandomShutdown
2024-04-19T09:02:57.8529652Z [2024/04/19 09:02:57.852 +00:00] [WARN] [grpclog.go:46] ["[core][Channel #163 SubChannel #166] grpc: addrConn.createTransport failed to connect to {Addr: \"127.0.0.1:34669\", ServerName: \"127.0.0.1:34669\", }. Err: connection error: desc = \"transport: Error while dialing: dial tcp 127.0.0.1:34669: connect: connection refused\""]
2024-04-19T09:02:59.3457353Z [2024/04/19 09:02:59.345 +00:00] [INFO] [server.go:174] ["closing tso server ..."]
```

### CI link
https://github.com/tikv/pd/actions/runs/8751050232/job/24015860152

### Reason for failure (if possible)

### Anything else