remote_bridge_loop: prevent segfault when after transfer of IAX2 of DAHDI call

remote_bridge_loop: prevent segfault when after transfer of IAX2 of DAHDI call

If the channel condition is one of the following after breaking out of the loop, don't try to update_peer
(where x = 0/1)
 1). ZOMBIE
 2). cx->tech_pvt != pvtx
 3). gluex != ast_rtp_instance_get_glue(cx->tech->type))

(closes issue #18781)
Reported by: alecdavis
Patches:
      bug18781.diff3.txt uploaded by alecdavis (license 585)
Tested by: alecdavis, ZX81

Review: https://reviewboard.asterisk.org/r/1128/

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@310287 65c4cc65-6c06-0410-ace0-fbb531ad65f3