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>