Automatic merge from submit-queue (batch tested with PRs 47776, 46220, 46878, 47942, 47947)
Add statefulset to the completion candidates of kubectl scale
**What this PR does / why we need it**: This commit adds `statefulset` to the completion candidates of kubectl scale.
```
$ kubectl scale <tab>
deployment job --replicas replicaset replicationcontroller statefulset
```
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixeskubernetes/kubectl#14
**Special notes for your reviewer**:
**Release note**:
```release-note
NONE
```
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