Always use the value of the AGISIGHUP when running an AGI.

Prior to this patch, the value of AGISIGUP was not always
honored when set on a channel.

(closes issue #13711)
Reported by: fmueller
Patches:
      13711.patch uploaded by putnopvut (license 60)



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@166470 65c4cc65-6c06-0410-ace0-fbb531ad65f3