Cannot accept video call request from another InCallService.

If another InCallService accepts an incoming video request, the incall UI
will not dismiss the glowpad, even those the call upgrades to video.

To correct this, added code in InCall.Call to detect changes to the
video state and set the SessionModificationState to "NO_REQUEST" should
a change occur while the call is in a RECEIVED_UPGRADE_TO_VIDEO_REQUEST
state.  This causes the glowpad and notification to dismiss.

Bug: 20958105
Change-Id: Id87c323b8b9defd674b49ce1ee9c2ad1a9a28341