Unregister scan client when RemoteException raises

When a remote exception is thrown while delivering
scan results, stop scanning and unregister the client.

As we marked "appDied=true", the client will be
unregistered while stop scanning.

Bug: 320223821
Bug: 320402249
Test: atest GattServiceTest ScanManagerTest &&
 manually crash apps multiple times to check

Change-Id: I570ed270751ad0cb47a8da37154873536ab24b3c