app_queue: add RINGCANCELED log event on caller hang up

QueueLog did not log ringnoanswer when the caller abandoned call
before first timeout. It was impossible to get agent membername
and ringing duration for this short calls. After some discusions
it seems that the best way is to add new event RINGCANCELED,
which is generated after caller hangup during ringing.

ASTERISK-26665

Change-Id: Ic70f7b0f32fc95c9378e5bcf63865519014805d3