LeConnectionOrientedChannel enters invalid state in race condition

LeConnectionOrientedChannel has a race condition:
1. Call `disconnect` and enter state `DISCONNECTING`
2. Receive `on_disconnection_request` and enter state `DISCONNECTED`
3. Receive `on_disconnection_response` and see that state is not `DISCONNECTING`, log invalid state and return

Not sure what the best solution is here, but it seems valid (though unlikely) that one might receive a disconnection request before `disconnect` is done processing.