Fix the device on "Media devices" wouldn't update

- This CL use new CachedBluetoothDevice callback instance
  in construct to avoid unregister wrong callback.
- This CL use flag to make sure preference will register
  callback on onAttached() when preference remove callback
  on onPrepareForRemoval() or onDetached().
- Update test case

Bug: 168682778
Bug: 157653997
Test: make -j42 RunSettingsRoboTests
Change-Id: I7a0d9f5332153ee80634e191847b84cd7c380b7d