Occasional failed unit test cases

[SeanHai]

Describe the bug (描述bug)

version: master
utest: RaftCliService2Test.ChangePeerTest (curvefs/test/metaserver/copyset/raft_cli_service2_test.cpp)

CI：http://59.111.91.248:8080/job/curve_untest_job/8131/console

The ChangePeerTest utest may occasionally fail.

To Reproduce (复现方法)

Expected behavior (期望行为)

Versions (各种版本)
OS:
Compiler:
branch:
commit id:

Additional context/screenshots (更多上下文/截图)