[GATE-55] More festive not-in-roster work.  At this point I'm reasonably confident that the listeners are doing the same work listening for presence packets was doing.

git-svn-id: http://svn.igniterealtime.org/svn/repos/wildfire/trunk/src/plugins/gateway@5788 b35dd754-fafc-0310-a699-88a17e54d16e