Cherry-picked from master.
Update APIs to access foregroudCalls, backgroudCalls, and ringingCalls
* 1. APIs to access list of calls
* 2. APIs to check if any active call, which has connection other than
* disconnected ones, pleaser refer to Call.isIdle()
* 3. APIs to return first active call
* 4. APIs to return the connections of first active call
* 5. APIs to return other property of first active call
Change-Id: Ic30e28018d14e496e9427f96fec8a7c2ff7c1549
4de9d20260