mount: Fix compilation after previous comment

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

mount.c

@@ -2372,7 +2372,7 @@ int collect_mnt_namespaces(bool for_dump)
 	arg.for_dump = for_dump;
 	arg.need_to_validate = false;
 
-	ret = walk_namespaces(&mnt_ns_desc, false, collect_mntns, &need_to_validate);
+	ret = walk_namespaces(&mnt_ns_desc, false, collect_mntns, &arg);
 	if (ret)
 		goto err;