Clarify CUT code, and in the process, fix a bug in trunk only

(closes issue #15320)
 Reported by: chappell
 Patches: 
       cut_fix.patch uploaded by chappell (license 8)
       cut_clarify.patch uploaded by chappell (license 8)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@201745 65c4cc65-6c06-0410-ace0-fbb531ad65f3