change server lookup method

[imaginator]

Problem:

• a site has delegated their XMPP service out to a third party. For example: university.edu using Google Apps for Domains and Google now provides XMPP for university.edu
• users like joined up identities: email address = IM address = buddycloud address

Right now to discover the buddycloud server for a domain:

• srv lookup for XMPP server for a domain
• connect to XMPP server
• disco for buddycloud component

The proposed solution would have the buddycloud-server discovering other buddycloud-servers by doing the equivalent of

• SRV query for _buddycloud-server._tcp.university.edu and retrieve buddycloud.non-google-xmpp-server.university.edu. (aka use DNS for discovery and avoid DISCO)