Automatic merge from submit-queue (batch tested with PRs 52831, 52764, 52763, 52673, 52558). 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>..
Minor fix: make sure that glusterfsPlugin implements interface ExpandableVolumePlugin
Attempting an assignment to make sure that `glusterfsPlugin` implements interface `ExpandableVolumePlugin`, just as we did for `DeletableVolumePlugin`, `PersistentVolumePlugin`
**What this PR does / why we need it**:
**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
```
/assign @gnufied