AudioAudioPolicyFocusListener and ducking enforced by framework

Notify AudioPolicyFocusListener an app received
  AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK even when focus is enforced by
  the framework.

Test: see bug
Bug: 37241497
Change-Id: I569e6611fb398955adbcd5bbfbda9d44db4aa729

services/core/java/com/android/server/audio/FocusRequester.java

@@ -381,6 +381,8 @@ public class FocusRequester {
                         Log.v(TAG, "NOT dispatching " + focusChangeToString(mFocusLossReceived)
                             + " to " + mClientId + ", ducking implemented by framework");
                     }
+                    mFocusController.notifyExtPolicyFocusLoss_syncAf(
+                            toAudioFocusInfo(), false /* wasDispatched */);
                     return; // with mFocusLossWasNotified = false
                 }