No need to post FGS notifications after process death

If the app dies during the deferral, we don't actually need to post the
FGS notification.  Since some of the service-related bookkeeping gets
reset as part of teardown, this avoids potential invalid accesses.

Bug: 197070543
Bug: 200555680
Test: atest CtsAppTestCases:android.app.cts.ServiceTest
Test: atest CtsAppTestCases:android.app.cts.NotificationManagerTest
Change-Id: I8a5eb91bb6070910ac973c195d118962265aec05