rabbit_networking: Take IP address from #listener{} instead of guessing

[Why]
Some systems use explicit distinct listeners for IPv4 and IPv6 (for
instance, FreeBSD). Other system will listen to IPv4 implicitly when
listening on IPv6 (for instance, Linux).

RabbitMQ works on both systems already, but `ranch_ref/1` was trying to
guess the IP address of a given listener based on its TCP port. Of
course, for two distinct listeners using the same TCP port, the result
was always the same IP address.

[How]
The #listener{} record already contains the IP address. Let's just use
it, instead of guessing.

Author: dumbbell

deps/rabbit/src/rabbit_networking.erl

@@ -197,8 +197,7 @@ tcp_listener_spec(NamePrefix, {IPAddress, Port, Family}, SocketOpts,
      transient, infinity, supervisor, [tcp_listener_sup]}.
 
 -spec ranch_ref(#listener{} | [{atom(), any()}] | 'undefined') -> ranch:ref() | undefined.
-ranch_ref(#listener{port = Port}) ->
-    [{IPAddress, Port, _Family} | _] = tcp_listener_addresses(Port),
+ranch_ref(#listener{ip_address = IPAddress, port = Port}) ->
     {acceptor, IPAddress, Port};
 ranch_ref(Listener) when is_list(Listener) ->
     Port = rabbit_misc:pget(port, Listener),