Omx: Fix codec instance leak if Observer dies

If Observer dies, {instance, observer} book-keeping may be
cleaned up. In such case avoid only unlinking the death-notifier,
but proceed with instance cleanup

Test: Manual use of Camera, Photos, Play Movies and YouTube.
Test: Small CtsMediaTestCases

Bug: 38149818
Change-Id: I412953b55827c93730353a95560b865fb18b5f0f
1 file changed