files-reg: make error message in clean_one_remap contain mntns path

rmntns_root - is fd number of opened mntns root directory, these info
doesn't help to identify mntns involved in logs, show path to these
mntns instead.
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@gmail.com>

criu/files-reg.c

@@ -681,7 +681,7 @@ static int clean_one_remap(struct remap_info *ri)
 	ret = unlinkat(rmntns_root, remap->rpath, remap->is_dir ? AT_REMOVEDIR : 0);
 	if (ret < 0) {
 		close(rmntns_root);
-		pr_perror("Couldn't unlink remap %d %s", rmntns_root, remap->rpath);
+		pr_perror("Couldn't unlink remap %s %s", path, remap->rpath);
 		return -1;
 	}
 	close(rmntns_root);