Patch for presence plugin to support query of 'self'

If Presence visibility is set to Subscribed, then it’s not possible to query ones OWN presence. We’re using the plugin from a server and this gives unavailable.

http://host:9090/plugins/presence/status?jid=user@domain&req_jid=user@domain

which seems overly secure It’s because you are not in your own roster, so the call to presenceManager.canProbePresence() fails.

I patched the PresencePlugin.java to support query of self if in Subscribed mode.

Patch attached.

Thanks, filed as OF-529 , will probably commit shortly