Make fah user own /tmp/fah.

This is to support migration of installation from one user to another.

Ownership is changed before Langouste setup to satisfy Langouste requirements.
Make samba use fah user as guest account.

Reported-by: Rusty Bowling <bowlinra@hotmail.com>

'nobody' owning files in ~/fah/ creates management issues so
make sure that files copied via samba are owned by fah user.
fahinstall 2.20