Fix flaky legacy pod autoscaler test

The reactor in runTest is set to catch all actions, but eventually it
only handles CreateAction without checking action type which might fail
sometimes when Patch arrives. This fix ensures we handle only the
CreateAction.

pkg/controller/podautoscaler/legacy_horizontal_test.go

@@ -472,7 +472,11 @@ func (tc *legacyTestCase) runTest(t *testing.T) {
 		if tc.finished {
 			return true, &v1.Event{}, nil
 		}
-		obj := action.(core.CreateAction).GetObject().(*v1.Event)
+		create, ok := action.(core.CreateAction)
+		if !ok {
+			return false, nil, nil
+		}
+		obj := create.GetObject().(*v1.Event)
 		if tc.verifyEvents {
 			switch obj.Reason {
 			case "SuccessfulRescale":