fixes an error in r203638 CEL commit

(closes issue #15525)
Reported by: elguero
Patches:
      iax2-double-unlock.patch uploaded by elguero (license 37)
      15525.diff uploaded by dvossel (license 671)
Tested by: dvossel



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@207225 65c4cc65-6c06-0410-ace0-fbb531ad65f3