Automatic merge from submit-queue (batch tested with PRs 42379, 42668, 42876, 41473, 43260)

Bump test coverage for initialresources

**What this PR does / why we need it**:

Increases test coverage for `plugin/pkg/admission/initialresources` to 80.2%.

**Which issue this PR fixes** 

https://github.com/kubernetes/kubernetes/issues/39559

**Special notes for your reviewer**:

Some of these features require E2E tests to achieve 100% coverage, the tests here are just unit tests, so I've tried to delineate as much as possible. I also saw that we might be exporting a lot of this to Heapster in the future.

**Release note**:

```release-note
Test coverage for initialresources increased to 80.2% percent.
```