Reference leaks in app_queue.

Reference leaks in app_queue.

* Fixed load_realtime_queue() leaking a queue reference when it overwrites
q when processing a realtime queue.
(issue ASTERISK-18265)

* Make join_queue() unreference the queue returned by
load_realtime_queue() when it is done with the pointer.  The
load_realtime_queue() returns a reference to the just loaded realtime
queue.

* Fixed queues container reference leak in queues_data_provider_get().

* queue_unref() should not return q that was just unreferenced.

* Made logic in __queues_show() and queues_data_provider_get() when
calling load_realtime_queue() easier to understand.

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@332874 65c4cc65-6c06-0410-ace0-fbb531ad65f3