Fix bug where final queue member would not be removed from memory.

Fix bug where final queue member would not be removed from memory.

If a static queue had realtime members, then there could be a potential
for those realtime members not to be properly deleted from memory.

If the queue's members were loaded from realtime and then all the
members were deleted from the backend, then the queue would still
think these members existed. The reason was that there was a short-
circuit in code such that if there were no members found in the
backend, then the queue would not be updated to reflect this.

Note that this only affected static queues with realtime members.
Realtime queues with realtime members were unaffected by this issue.

(closes issue ASTERISK-19793)
reported by Marcus Haas
........

Merged revisions 371306 from http://svn.asterisk.org/svn/asterisk/branches/1.8

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/10@371313 65c4cc65-6c06-0410-ace0-fbb531ad65f3