Ensure LE scan clients are removed when the related app dies

Use the passed in ScanClient in handleStopScan() to ensure that the
client appDied flag is in the correct state to ensure proper removal of
the client application reference.

Bug: 30681588
Test: manual
Change-Id: I0e0067a8e21ebd5f89870a7054b1f4092fe63ae1
(cherry picked from commit a75cf68a)