Don't duplicate variables on the sip_pvt. Just reset the variable list each
time.
(closes issue #19202)
Reported by: wdoekes
Patches:
issue19202_destroy_challenged_invite_chanvars.patch uploaded by wdoekes (license 717)
git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@317867 65c4cc65-6c06-0410-ace0-fbb531ad65f3