IMS-VT: Support QTI audio routing policy for modify/merge calls

- Audio policy is to turn SPEAKER on if the user makes any action that
  indicates a transition to video calls or route to EARPICE for voice
  calls. For all other non-user initiated transitions, no changes are
  made in the audio routing path.

- Handle all user initiated (MO) upgrade/downgrade requests, merge calls
  , user accepted (MT) upgrade requests and incoming call in this change.
  Other use cases like outgoing calls, add call, call waiting are
  handled in Telecomm layer.

- Only make changes to audio route if Bluetooth or wired headset is
  not connected.

IMS-VT: Route to speaker if current route is not BT, headset or speaker

- Route audio to speaker(/earpiece) only if current audio route is
  not bluetooth, wired headset or speaker(/earpiece)

Change-Id: Id5b1910487d8f365ca5c449c3e62ef24d6f3b530
CRs-Fixed: 879183 932268