Bluetooth: Add convenience method to convert connection state to string

* Add method to convert the following state values to string
  - BluetoothHeadset.STATE_DISCONNECTED
  - BluetoothHeadset.STATE_CONNECTING
  - BluetoothHeadset.STATE_CONNECTED
  - BluetoothHeadset.STATE_DISCONNECTING

Test: make
Change-Id: Iaa5b6e35d3214ded8edbe29d626e0869651417d1
1 file changed
tree: 5e1b43be55a7fa5f346dd37513fd1a24a733fd61
  1. framework/
  2. service/