Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
pkg/securitycontext/util_test.go(TestAddNoNewPrivileges): update tests
**What this PR does / why we need it**:
This PR improves existing test in the following ways:
- remove irrelevant test cases
- add test case for `AllowPrivilegeEscalation: nil`
- explicitly specify input and expected outcome
This is addressed to the following review comment: https://github.com/kubernetes/kubernetes/pull/47019#discussion_r135808264
**Release note**:
```release-note
NONE
```
PTAL @jessfraz @kubernetes/sig-auth-pr-reviews
CC @simo5
8a6bb3e120