MEDIUM: stream-int: queue idle connections at the server

Now we get a per-server list of all idle connections. That way we'll
be able to reclaim them upon shortage later.
diff --git a/src/stream_interface.c b/src/stream_interface.c
index 4b8d924..2ea59c7 100644
--- a/src/stream_interface.c
+++ b/src/stream_interface.c
@@ -515,6 +515,7 @@
 
 	if (conn->flags & (CO_FL_ERROR | CO_FL_SOCK_RD_SH)) {
 		/* warning, we can't do anything on <conn> after this call ! */
+		LIST_DEL(&conn->list);
 		conn_force_close(conn);
 		conn_free(conn);
 		si->end = NULL;