The etcd client to the registry of Pump/Drainer info does not use auto-sync and fails when the PD cluster address changed

[lance6716]

copied from pingcap/tidb#42643

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Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1. Start a TiDB cluster with 3 PDs ① ② ③ and a Pump connected
2. Scale-out 3 more PDs ④ ⑤ ⑥
3. Wait 31 seconds
4. Scale-in the original PDs ① ② ③
5. Wait 31 seconds
6. Run SHOW PUMP STATUS;

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

We see the status of the pump at step 6

3. What did you see instead (Required)

Context deadline exceeded in etcd.(*Client).List

4. What is your TiDB version? (Required)

v4.0.14