Bug 876335 - Update additional information by HandledCall itself

https://bugzilla.mozilla.org/show_bug.cgi?id=876335

When initializing the handled call of the second incoming call, CallScreen.activeCall is still the node the first call. Which results to that the additional information of the node representing the first call is altered with the information of the second call.

In this patch we let HandleCall update the additional information by itself. In addition to it, remove the 'resumed' case (which is not existing) and fix the CallScreen.activeCall function.