MINOR: stream: pass the pointer to the origin explicitly to stream_new()

We don't pass sess->origin anymore but the pointer to the previous step. Now
it should be much easier to chain elements together once applets are moved out
of streams. Indeed, the session is only used for configuration and not for the
dynamic chaining anymore.
diff --git a/src/peers.c b/src/peers.c
index 084a97b..0676120 100644
--- a/src/peers.c
+++ b/src/peers.c
@@ -1140,7 +1140,7 @@
 	}
 	t->nice = l->nice;
 
-	if ((s = stream_new(sess, t)) == NULL) {
+	if ((s = stream_new(sess, t, &appctx->obj_type)) == NULL) {
 		Alert("Failed to initialize stream in peer_session_create().\n");
 		goto out_free_task;
 	}