Distinguish between NAP and PANU disconnect in BT tethering
and call appropriate functions. We were never disconnecting
NAP role devices.
ToDo: BluetoothService needs to be refactored, its become too big
1) BluetoothAdapter and BluetoothDevice properties need to be moved to separate
classes.
2) BluetoothPanProfile and BluetoothInputDeviceProfile which are handled
by BluetoothService need to be moved to a separate file.
3) Integrate PAN to the profile state machine.
Change-Id: I32a8d274f38c78931434bd9738c8f6570ba89fcf
a44a1e77ef