Don't call adjustFocusedActivityStackLocked on finished activity.

When an activity is finished, adjustFocusedActivityStackLocked is
already called on the associated record and the task association is
lost. Calling it again is redundant and leads to a crash as we
assume the task is still associated with the activity.

Change-Id: Ie7cc9ad8b1542d7415b7409e539c88d3b4ec8dcd
Fixes: 37329424
Test: bit FrameworksServicesTests:com.android.server.am.ActivityStackTests#testStopActivityWhenActivityDestroyed