Drop video calls when data is disabled.

Handle dropping of video calls for one of two reasons:
1. User disables data.
2. User exceeds the data limit policy on their device.

In both cases, terminate any ongoing video calls.  Ensures the correct
disconnect cause is propagated up to the InCallService.

Bug: 30702393
Change-Id: I36d236c8f69f9dc5b17368cc5329ac1df991fac4