Fix skinny debug tab completion

Review the syntax of the 'skinny debug' command to show more than
just 'show' for options to 'skinny debug' command.

(closes issue ASTERISK-20789)
Reported by: snuffy
Tested by: snuffy, myself
Patches:
    skinny-debug.diff uploaded by snuffy (license 5024)
........

Merged revisions 377985 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@377986 65c4cc65-6c06-0410-ace0-fbb531ad65f3