drbd_set_role needs to bail out if the state change failed

fix for bug#252
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

drivers/block/drbd/drbd_nl.c

@@ -344,6 +344,9 @@ int drbd_set_role(struct drbd_conf *mdev, enum drbd_role new_role, int force)
 		break;
 	}
 
+	if (r < SS_SUCCESS)
+		goto fail;
+
 	if (forced)
 		dev_warn(DEV, "Forced to consider local data as UpToDate!\n");