Race Flake in TestControllerSyncFleetAutoscaler() (#3260)

Weird that this has more consistently failed with the Go race condition
checker failing on this test recently -- but it's a test we wrote a
while ago!

The flake was that the test added a Reactor to the mock _after_ the
Informer system had been started - which caused a race condition inside
the Fake client system as different systems interacted with the mock.

Changing the order fixes the issue!

pkg/fleetautoscalers/controller_test.go

@@ -756,14 +756,14 @@ func TestControllerSyncFleetAutoscaler(t *testing.T) {
 		t.Parallel()
 
 		c, m := newFakeController()
-		ctx, cancel := agtesting.StartInformers(m, c.fleetSynced, c.fleetAutoscalerSynced)
-		defer cancel()
-
 		m.AgonesClient.AddReactor("get", "fleetautoscalers", func(action k8stesting.Action) (bool, runtime.Object, error) {
 			ga := action.(k8stesting.GetAction)
 			return true, nil, k8serrors.NewNotFound(corev1.Resource("gameserver"), ga.GetName())
 		})
 
+		ctx, cancel := agtesting.StartInformers(m, c.fleetSynced, c.fleetAutoscalerSynced)
+		defer cancel()
+
 		require.NoError(t, c.syncFleetAutoscaler(ctx, "default/fas-1"))
 	})
 }