Implement function that drops privileges by:

• chrooting to /var/empty (user hast home directory),
• setting groups to 'hast' (user hast primary group),
• setting real group id, effective group id and saved group id to 'hast',
• setting real user id, effective user id and saved user id to 'hast'.

At the end verify that those operations where successfull.

MFC after: 1 week