The ansible vars fail on CI because the validate arguments task runs way
before the setting of the variables, which causes the ansible undefined
vars on CI to cause errors.

This is a way better approach of having the static values as defaults
and allowing setting the variables to ansible vars in the host/group vars

The pihole lookup DNS queries when the VPN connection is up was slow.
One of the culprits was the quad9 servers were taking long time when
using VPN
The other issue was the previous routing tables that used to work with
the fritzbox (with DHCP) which wasn't fully working was conflicting with
the VPN route tables and causing loops and delays.

Now most of the VPN queries are working fast but some requests are
taking some time, probably due to the VPN trying to check/block ads and
malware!

Also minor fixing to the pre tasks and documentation