This program doesn't parse /etc/fstab or /etc/mtab,
it just calls the umount2 syscall.

It is another attempt to fix the error:
subprocess.CalledProcessError: Command '['mount', '--make-private', '/tmp/criu-root-C7MZS9']' returned non-zero exit status 1
OSError: [Errno 16] Device or resource busy: '/tmp/criu-root-C7MZS9'
Signed-off-by: Andrei Vagin <avagin@openvz.org>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>