Audio routing fixes for handover scenarios.

1) Change maybeMoveToSpeakerPhone so when initiating a handover to
a self-managed CS for a video call, we do not enter speakerphone until
the call goes active (this is when the handover is accepted).  This
ensures we don't go to speaker even if the handover is rejected.
2) Modify processIncomingCallIntent to automatically go to speakerphone
on the receiving side of a handover once the call goes active.

Test: Manual
Bug: 37772102
Change-Id: I2617ff19681eec2a54faa210a5a73e8a29d6126c