Restoring mount namespaces requires to create temporary directories
in a test root.

When tests execute in a new userns, they have non-zero gid and uid,
so we need to grant permissions for them.

v2: add +rx as well

Reported-by: Mr Jenkins
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>