Automatic merge from submit-queue (batch tested with PRs 51114, 51233, 51024, 51053, 51197)
add UT for pkg/apis/autoscaling/v2alpha1/defaults.go
**What this PR does / why we need it**:
add UT for pkg/apis/autoscaling/v2alpha1/defaults.go
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #
**Special notes for your reviewer**:
**Release note**:
```release-note
None
```