res/ari/resource_channels: Add missing 'no_answer' reason to DELETE /channels

One of the canonical reasons for hanging up a channel is because the far end
failed to answer - or because someone else answered, and we want to get rid of
this channel. This patch adds the missing value to the 'reason' query parameter
for the DELETE /channels operation.

Review: https://reviewboard.asterisk.org/r/4400

ASTERISK-24745 #close
Reported by: Ben Merrills
patches:
  add_no_answer_ari_hangup_cause.diff uploaded by Ben Merrills (License 6678)
........

Merged revisions 431622 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@431623 65c4cc65-6c06-0410-ace0-fbb531ad65f3