Bug 1016277 - If two different apps try to use the 'telephony' channel at the same time both apps can play audio.

See bug https://bugzilla.mozilla.org/show_bug.cgi?id=1016277 please.

These are the Loop app bits we need to add if we want the Loop app to compete correctly for the telephony audio channel.
Let's expose this in order to call it directly from the `callscreen`