Merge pull request #27151 from caesarxuchao/gc-e2e

Automatic merge from submit-queue

[garbage collector] add e2e test

This PR also includes some changes to plumb controller-manager's `--enable_garbage_collector` from the environment variable.

The e2e test will not be run by the core suite because it's marked `[Feature:GarbageCollector]`.

The corresponding jenkins job configuration PR is https://github.com/kubernetes/test-infra/pull/132.

pkg/controller/garbagecollector/garbagecollector.go

@@ -684,6 +684,7 @@ func (gc *GarbageCollector) processItem(item *node) error {
 }
 
 func (gc *GarbageCollector) Run(workers int, stopCh <-chan struct{}) {
+	glog.V(0).Infof("GarbageCollector is starting running!")
 	for _, monitor := range gc.monitors {
 		go monitor.controller.Run(stopCh)
 	}