cr-check: add userns/loginuid checks to extra features

All kernel options, features that depend on kernel version
should be checked with `criu check`.

Cc: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>