fix unstable ut; 修复不稳定的单测

[seeflood]

What would you like to be added:
The UT in components/lock/zookeeper/zookeeper_lock_test.go is not stable. Sometimes some lines of components/lock/zookeeper/zookeeper_lock.go are not covered in the UT and will lead to decreased test coverage.
For example , codecov reports it in #678 (comment)

It's because some code runs in a seperated goroutine. At the end of the test, the goroutine has not been executed:

We should make the test coverage stable

Why is this needed:
No more codecov warning

[ZLBer]

@seeflood who make who fix 😅

[seeflood]

This issue is one of the tasks in #654 and you can get some presents after fixing it