fix crash when try lock raftLock, enable balance by experimental

[critical27]

What type of PR is this?

• bug
• feature
• enhancement

What problem(s) does this PR solve?

Issue(s) number:

Description:

Crashed because we check the mutex whether is held. As for leader, sometimes, we could pass the check in commitRemovePeer, but we may fail in removePeer or updateQuorum.

How do you solve it?

Explicitly lock the function when necessary (as for leader). Follower don't need to lock it because the lock has already been acquired outside the function.

Special notes for your reviewer, ex. impact of this fix, design document, etc:

Checklist:

Tests:

• Unit test(positive and negative cases)
• Function test
• Performance test
• N/A

Affects:

• Documentation affected (Please add the label if documentation needs to be modified.)
• Incompatibility (If it breaks the compatibility, please describe it and add the label.）
• If it's needed to cherry-pick (If cherry-pick to some branches is required, please label the destination version(s).)
• Performance impacted: Consumes more CPU/Memory

Release notes:

Please confirm whether to be reflected in release notes and how to describe:
Not related