Bug 1094878 - Call is not on hold anymore after hanging up another call even though the icon says it is

It seems that all that's needed for this test is the following:
```
    913       test('should resume the conference call if not put on hold by the user',
    914       function() {
    915         this.sinon.spy(MockNavigatorMozTelephony.conferenceGroup, 'resume');
    916
    917         // Add extra call.
    918         telephonyAddCall.call(this, extraCall, {trigger: true});
    919         // Hang up the extra call.
    920         MockNavigatorMozTelephony.calls = [];
    921         MockNavigatorMozTelephony.mTriggerCallsChanged();
    922
    923         sinon.assert.called(MockNavigatorMozTelephony.conferenceGroup.resume);
    924       });
```