MEDIUM: protocol: explicitly start the receiver before the listener

MEDIUM: protocol: explicitly start the receiver before the listener

Now protocol_bind_all() starts the receivers before their respective
listeners so that ultimately we won't need the listeners for non-
connected protocols.

We still have to resort to an ugly trick to set the I/O handler in
case of syslog over UDP because for now it's still not set in the
receiver, so we hard-code it.