Make changes to CARSM and BRM for multi-hfp

* Update the BRM <-> CARSM interface
* Update CARSM to no longer actively connect to BT in state enter()
methods. Instead rely on messages from BRM to enter
ActiveBluetoothRoute.

Test: unit tests updated
Change-Id: Id9bf507fb4f813e1bfcce5571d61b3819e55adf3