REORG: listener: move the listening address to a struct receiver

The address will be specific to the receiver so let's move it there.
diff --git a/src/session.c b/src/session.c
index c303585..871a6ac 100644
--- a/src/session.c
+++ b/src/session.c
@@ -220,7 +220,7 @@
 	}
 
 	/* Adjust some socket options */
-	if (l->addr.ss_family == AF_INET || l->addr.ss_family == AF_INET6) {
+	if (l->rx.addr.ss_family == AF_INET || l->rx.addr.ss_family == AF_INET6) {
 		setsockopt(cfd, IPPROTO_TCP, TCP_NODELAY, (char *) &one, sizeof(one));
 
 		if (p->options & PR_O_TCP_CLI_KA) {