process_agent_dial_outcome only recognized hangup causes 17/18/19/21/34/38.
When the reserved agent's AOR has zero registered contacts (e.g. the
softphone dropped, or nobody ever registered), Asterisk immediately
hangs up with cause 3 (no route to destination) instead of running a
Dial() long enough to produce a DialEnd/NOANSWER at all - so the retry
listener silently ignored it and the escalation was left dangling in
'ringing' status (the agent itself still got released via the
call-ended fallback path, but no retry to the next agent was ever
attempted and the escalation record never reflects the failure).
Added causes 1 (unallocated number), 3 (no route), 20 (subscriber
absent), 22 (number changed) alongside the existing set.
arys