(closes issue #10688)

Reported by: casper
Patches:
      chan_sip.c.82076.diff uploaded by casper (license 55)
Remove double check for zombie flag and optimize things a bit.


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@82077 65c4cc65-6c06-0410-ace0-fbb531ad65f3