Minor cleanups & Move appending PARRTUUID to a %post action in the ks

Minor cleanups

• RPI's do not have a bootlaoder known by linux distro's
• chrony is already enabled @services
• remove script for wifi fix, it is already done @image creation
• rootfs-expand needs root privileges

_Group sections in functional order _ (Note this does not change anything, to me this workflow makes the ks more readable)

• first all system related tweaks
• second user creation
• last cleanup

Clean yum cache

• should reduce size shipped compressed image

Refactor default user creation

• FIXME: why does the kickstart fail to create a user with appliance-tools?

Move PARRTUUID to a %post action in the ks

• also chown the result ro the $SUDO_USER if ran with sudo