Channel names should be different from other channels in the system while
the channel exists.

* Use a sequence number for CBRec channels instead of a random number
because the same random number could be picked again for the next CBRec
channel.
........

Merged revisions 431052 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@431053 65c4cc65-6c06-0410-ace0-fbb531ad65f3