Correct some scenarios where CALL_LIMIT could not be getting adjusted...

 Correct some scenarios where CALL_LIMIT could not be getting adjusted properly allowing chan_sip to send calls when it really shouldn't. Bug #6111


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@8432 65c4cc65-6c06-0410-ace0-fbb531ad65f3