Call enqueueWork on resource deletion (#1048)
Call enqueueWork on resource deletion (#1048)

Some controllers need to clean up state when resources are deleted.

If an object is deleted before the informer can retrieve its final
state, the event handler receives an object of type
DeletedFinalStateUnknown. To handle that properly, we need to call
DeletionHandlingMetaNamespaceKeyFunc() instead of the standard
MetaNamespaceKeyFunc().
knative/serving,knative/serving