MINOR: receiver: link the receiver to its settings

Just like listeners keep a pointer to their bind_conf, receivers now also
have a pointer to their rx_settings. All those belonging to a listener are
automatically initialized with a pointer to the bind_conf's settings.
diff --git a/src/listener.c b/src/listener.c
index 1a8b5ad..ef9b7d0 100644
--- a/src/listener.c
+++ b/src/listener.c
@@ -563,7 +563,7 @@
 		LIST_ADDQ(&bc->frontend->conf.listeners, &l->by_fe);
 		LIST_ADDQ(&bc->listeners, &l->by_bind);
 		l->bind_conf = bc;
-
+		l->rx.settings = &bc->settings;
 		l->rx.fd = fd;
 		memcpy(&l->rx.addr, ss, sizeof(*ss));
 		MT_LIST_INIT(&l->wait_queue);