pkg/oom/v2: handle EventChan routine shutdown quietly

When the cgroup is removed, EventChan is closed (this was pulled in by
8d69c041c5). This results in a nil error
being received. Don't log an error in that case but instead return.

Signed-off-by: Jeremi Piotrowski <jpiotrowski@microsoft.com>

pkg/oom/v2/v2.go

@@ -102,10 +102,13 @@ func (w *watcher) Add(id string, cgx interface{}) error {
 				i.ev = ev
 				w.itemCh <- i
 			case err := <-errCh:
+				// channel is closed when cgroup gets deleted
+				if err != nil {
 					i.err = err
 					w.itemCh <- i
 					// we no longer get any event/err when we got an err
 					logrus.WithError(err).Warn("error from *cgroupsv2.Manager.EventChan")
+				}
 				return
 			}
 		}