Avoid a NullPointerException in getDevicesMatchingConnectionStates

In the method of getDevicesMatchingConnectionStates, use local variables repeat mAdapterService.
to avoid to mAdapterService is NullPointerException

Fixes:120749867
Test: manual
  1. Turn on Bluetooth and connect to the Bluetooth headset.
  2. Disconnect the connected Bluetooth headset from DUT and turn off Bluetooth.
  3. Repeat step 1 and step 2

Change-Id: I4afa346d937b2fca40c59d5985efdf384be1fc99