Android: Implement QLEService::characteristicChanged() for peripheral mode

Emits the above signal when the remote client successfully updates
a characteristic.

Change-Id: I236b1f92b682028bc10be798192f46bffc981101
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>
Reviewed-by: Alex Blasche <alexander.blasche@qt.io>