Synchronously call callback when load is cancelled

This prevents the case when controller unbinds and nulls the provider
used by the callback with a slight delay. Callback is ignored when there
is no provider and ControlsController gets stuck in seeding state.

Test: manual with the steps from the comment#18
Test: atest ControlsBindingControllerImplTest
Fixes: 283888863
Change-Id: I5683170b71ad47702c924fbb2df293118937cb37

packages/SystemUI/src/com/android/systemui/controls/controller/ControlsBindingControllerImpl.kt

@@ -312,6 +312,7 @@ open class ControlsBindingControllerImpl @Inject constructor(
                 Log.d(TAG, "Canceling loadSubscribtion")
                 it.invoke()
             }
+            callback.error("Load cancelled")
         }
 
         override fun onSubscribe(token: IBinder, subs: IControlsSubscription) {

packages/SystemUI/tests/src/com/android/systemui/controls/controller/ControlsBindingControllerImplTest.kt

@@ -116,11 +116,7 @@ class ControlsBindingControllerImplTest : SysuiTestCase() {
 
     @Test
     fun testBindAndLoad_cancel() {
-        val callback = object : ControlsBindingController.LoadCallback {
-            override fun error(message: String) {}
-
-            override fun accept(t: List<Control>) {}
-        }
+        val callback = mock(ControlsBindingController.LoadCallback::class.java)
         val subscription = mock(IControlsSubscription::class.java)
 
         val canceller = controller.bindAndLoad(TEST_COMPONENT_NAME_1, callback)
@@ -130,6 +126,7 @@ class ControlsBindingControllerImplTest : SysuiTestCase() {
 
         canceller.run()
         verify(providers[0]).cancelSubscription(subscription)
+        verify(callback).error(any())
     }
 
     @Test