Bug 1079974 - [Loop] Ringer should be played through the main speaker

See bug https://bugzilla.mozilla.org/show_bug.cgi?id=1079974 please.
Why not both lines inside the <if> statement? This early return at the end of the method is not needed thought

```js
if (AudioCompetingHelper) {
  AudioCompetingHelper.leaveCompetition();
  AudioCompetingHelper.destroy();
}
```