Automatic merge from submit-queue

Fix startup type error in initializeCaches

The following error was getting logged:
PersistentVolumeController can't initialize caches, expected list of volumes, got:
&{TypeMeta:{Kind: APIVersion:} ListMeta:{SelfLink:/api/v1/persistentvolumes ResourceVersion:11} Items:[]}

The tests make extensive use of NewFakeControllerSource which uses api.List
instead of api.PersistentVolumeList. So use reflect to help iterate over the
items then assert the item type.

fixes #27757