RC/RS: Use ControllerRef to route watch events.

This is part of the completion of ControllerRef, as described here:

https://github.com/kubernetes/community/blob/master/contributors/design-proposals/controller-ref.md#watches

This also removes the need for the Pod->Controller mapping cache in RC
and RS. This mapping is now persisted in the Pod's ControllerRef
instead.

test/integration/replicaset/replicaset_test.go

@@ -143,7 +143,6 @@ func rmSetup(t *testing.T) (*httptest.Server, *replicaset.ReplicaSetController,
 		informers.Core().V1().Pods(),
 		clientset.NewForConfigOrDie(restclient.AddUserAgent(&config, "replicaset-controller")),
 		replicaset.BurstReplicas,
-		4096,
 	)
 
 	if err != nil {