Expand AGISTATUS variable to include NOTFOUND which is set when the AGI file...

Expand AGISTATUS variable to include NOTFOUND which is set when the AGI file could not be found. (issue #9285 reported by srdjan)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@70731 65c4cc65-6c06-0410-ace0-fbb531ad65f3