Automatically set up btrfs root and data filesystem, as well as external
HDD.
This automation change assumes a layout exactly as in current bob to
function by default, can be changed to any btrfs layout with the
`btrfs_mounts` configuration option, however.
If we only tag the geerlingguy docker 'role' as docker we do not always
install the necessary python dependencies for later working with ansible
docker compose and network roles.
Applying the docker tag to them we can target '--tags=docker' on
playbook run and be sure that all later roles will have the correct
dependencies.