Make sure top activity is stopped on sleep if paused.

Currently we have logic in place to handle moving a top resumed
activity to paused and eventually stopped if entering sleep. However,
we do not handle the case when the top activity is already paused.

This changelist addresses this issue by identifying this condition
and moving the activity to the stopped state.

Change-Id: I8d6f9282ff863cf8017f6d64ab60911fb1c376c2
Fixes: 65457314
Test: cts/hostsidetests/services/activityandwindowmanager/util/run-test CtsServicesHostTestCases android.server.cts.ActivityManagerDisplayTests#testExternalDisplayActivityTurnPrimaryOff