mod_pubsub_serverinfo: Detect existence of pub/sub node Instead of blindly trying to create the pub/sub node to publish items to, a service discovery query is performed to check if node creation is required. Added various bits of warn and debug logging, to give a user better feedback if and why something is failing.

local count_registering = module:measure("user_registering", "rate");
local count_registered = module:measure("user_registered", "rate");

module:hook("user-registering", function ()
	count_registering();
end);

module:hook("user-registered", function ()
	count_registered();
end);