Automatic merge from submit-queue

CRI: Refactor kuberuntime unit test

Based on https://github.com/kubernetes/kubernetes/pull/34858

This PR:
1) Refactor the fake runtime service and some kuberuntime unit test.
2) Add better garbage collection unit test.
3) Fix init container unit test which isn't testing correctly. Some other unit tests may also need to be fixed.
4) Add pod log directory garbage collection unit test.

@feiskyer @yujuhong 
/cc @kubernetes/sig-node