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/stats.c b/src/stats.c
index 36aee99..38cac0c 100644
--- a/src/stats.c
+++ b/src/stats.c
@@ -1535,8 +1535,8 @@
 		char str[INET6_ADDRSTRLEN];
 		int port;
 
-		port = get_host_port(&l->addr);
-		switch (addr_to_str(&l->addr, str, sizeof(str))) {
+		port = get_host_port(&l->rx.addr);
+		switch (addr_to_str(&l->rx.addr, str, sizeof(str))) {
 		case AF_INET:
 			stats[ST_F_ADDR] = mkf_str(FO_CONFIG|FS_SERVICE, chunk_newstr(out));
 			chunk_appendf(out, "%s:%d", str, port);