Automatic merge from submit-queue
simplify disruption controller finder logic
**What this PR does / why we need it**:
Address some comments from https://github.com/kubernetes/kubernetes/pull/45003 and simplify the PDB controller logic as part of issue https://github.com/kubernetes/kubernetes/issues/42284
@enisoc @kargakis @caesarxuchao
Also it feels like we can get rid of the finders all together since with controller ref, each pod has only controller. Let me know if i should remove that finders all together ?