Automatic merge from submit-queue (batch tested with PRs 50550, 50768)

Cleanup locking in configz

**What this PR does / why we need it**:
- Reduce scope of lock in `write()` method
- Use the read lock in `write()` method

**Release note**:
```release-note
NONE
```
/kind cleanup

@mikedanese 

p.s. looks like the `Set()` method could be removed if the value is accepted as an argument to `New()`. I.e. looks like to code re-sets the value.