mount: Close old service descriptor in mntns_collect_root

We're about to collect root several times in a row, so keeping
the old one isn't required.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

mount.c

@@ -1531,6 +1531,8 @@ int mntns_collect_root(pid_t pid)
 	int ret;
 	char path[PATH_MAX + 1];
 
+	close_service_fd(ROOT_FD_OFF);
+
 	if (!(current_ns_mask & CLONE_NEWNS)) {
 		/*
 		 * If criu and tasks we dump live in the same mount