Automatic merge from submit-queue (batch tested with PRs 42202, 40784, 44642, 44623, 44761)
make kubectl clientcache thread safe
**What this PR does / why we need it**:
Prevent panics when accessing kubectl client cache concurrently.
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #
https://github.com/kubernetes/helm/issues/1879