security: check additional groups,v5

Currently, we only check if process gids match primary gid of user.
But process and user have additional groups too. So lets:
     1) check that process rgid,egid and sgid are in the user's grouplist.
     2) on restore check that user has all groups from the images.

Signed-off-by: Ruslan Kuprieiev <kupruser@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
security: rename check_ids to check_uids and drop crid argument, v3

Currently check_ids is used to check uids only. So lets rename it
and drop crid argument, as we can use cr_uid directly.

Signed-off-by: Ruslan Kuprieiev <kupruser@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
test: security

This test creates 2 users to check how secure is using criu with setuid bit set.

Signed-off-by: Ruslan Kuprieiev <kupruser@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>