Fix tab completion when you just do a plain tab without entering anything, and...

Fix tab completion when you just do a plain tab without entering anything, and also fix show application tab completion. (issue #7089 reported by blitzrage)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@28792 65c4cc65-6c06-0410-ace0-fbb531ad65f3