Ensure non-ringing call doesn't start ringing.

Its possible for ringing to be triggered by a bluetooth state change; if
the call goes active while this is taking place, we can have a scenario
where the call is no longer ringing by the time the bluetooth change
takes place.

Test: Compile; log inspection.
Bug: 131980471
Change-Id: I9dfcd74cee3c2c94f63107987bfa5017f7b5c2c0