Calling Wake() on UDP conn does nothing

We are trying to echo messages received from one UDP connection to other connected UDP clients.  However, it looks like the UDP connection doesn't have an associated `loop`, so calling `Wake()` on the connection does nothing because loop is nil.
Should the connection created in `func loopUDPRead(s *server, l *loop, lnidx, fd int)` have a reference to the `loop`? 
