This adapts the README to describe the necessary tooling. And modifies
the test vm to use libvirt as provider (instead of vbox).
Runs fine as demonstrated in P802.
First iteration failed without the gpg dependency ~> P800 Thus why the
post-install.sh adds it directly as a workaround (in this diff).
Ideally, this should be added in our manifest somewhere or even better in the
puppet module which requires it but I don't know which one is pulling
it ¯\_(ツ)_/¯. In the mean time, that sounds reasonable.
Note: As P801 shows, it is not required for the vbox template and I don't know
why this worked for it.
Depends on D4137
Related to T2606