Because of how Ansible local relative search paths work, the global
"files" and "templates" directories need to be next to the playbooks.
However its not intuitive to look into the playbooks directory to find
the files and templates for a host.
Therefore flatten the playbooks directory to get rid of this confusing
structure.
Also see:
https://docs.ansible.com/ansible/latest/playbook_guide/playbook_pathing.html#resolving-local-relative-paths
Ensure NGINX repo and install on nginx_hosts before apt update, so that
the latest NGINX key is deployed and apt update won't fail on an invalid
signature on these hosts.
Also only run the gnupg install if gnupg isn't present in the nginx
repo_setup.yaml to make that work.
