criu: threads -- Allow uids/gids being different

We are carrying uids/gids in per-thread way since v1.8,
so no need to require them to match anymore. We still
require seccomp to match though. Need to revisit, seems
may relax this requirement as well.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>