PD `getMembers`'s timeout duration is not limited by the config.

[iosmanthus]

Bug Report

1. Describe the bug

While disconnecting with the PD servers, the client will not produce a timeout exception in time by the config.

2. Minimal reproduce step (Required)

1. Launch a workload with tiup playground.
2. execute shell command: pkill -SIGSTOP pd-server

3. What did you see instead (Required)

Some slow logs report that requests run about 22s, instead of the config duration.

4. What did you expect to see? (Required)

Report timeout in time.

5. What are your Java Client and TiKV versions? (Required)

• Client Java: 3.3.0 or master
• TiKV: any version