Automatic merge from submit-queue
return destroy func to clean up internal resources of storage
What?
Provide a destroy func to clean up internal resources of storage.
It changes **unit tests** to clean up resources. (Maybe fix integration test in another PR.)
Why?
Although apiserver is designed to be long running, there are some cases that it's not.
See https://github.com/kubernetes/kubernetes/issues/31262#issuecomment-242208771
We need to gracefully shutdown and clean up resources.
40efde7e0a