Ensure realtime conferences are treated the same as static conferences when trying to find an empty one.

Also, parse the useropts properly, when retrieving from realtime, and add them
to the existing flags.

(closes issue #17502)
 Reported by: kenji
 Patches: 
       20100720__issue17502.diff.txt uploaded by tilghman (license 14)
 Tested by: kenji


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@278463 65c4cc65-6c06-0410-ace0-fbb531ad65f3