Use RaceFreeFakeWatcher in ObjectTracker

The FakeWatcher allows sends on the result channel after it's closed,
for example calling Stop() then Add() will panic. RaceFreeFakeWatcher
checks whether the watcher is stopped before attempting to send. It also
panics instead of blocking when the result channel is full.

Kubernetes-commit: b84ad8828b6ffe0dd289f69e395968eabb9fbeaa

testing/fixture_test.go

@@ -190,3 +190,34 @@ func TestWatchCallMultipleInvocation(t *testing.T) {
 	}
 	wg.Wait()
 }
+
+func TestWatchAddAfterStop(t *testing.T) {
+	testResource := schema.GroupVersionResource{Group: "", Version: "test_version", Resource: "test_kind"}
+	testObj := getArbitraryResource(testResource, "test_name", "test_namespace")
+	accessor, err := meta.Accessor(testObj)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	ns := accessor.GetNamespace()
+	scheme := runtime.NewScheme()
+	codecs := serializer.NewCodecFactory(scheme)
+	o := NewObjectTracker(scheme, codecs.UniversalDecoder())
+	watch, err := o.Watch(testResource, ns)
+	if err != nil {
+		t.Errorf("watch creation failed: %v", err)
+	}
+
+	// When the watch is stopped it should ignore later events without panicking.
+	defer func() {
+		if r := recover(); r != nil {
+			t.Errorf("Watch panicked when it should have ignored create after stop: %v", r)
+		}
+	}()
+
+	watch.Stop()
+	err = o.Create(testResource, testObj, ns)
+	if err != nil {
+		t.Errorf("test resource creation failed: %v", err)
+	}
+}