Add support for API servers on IPv6 addresses (#48)

* Remove duplicate file for deletion

* Add support for IPv6 clusters

To correctly escape IPv6 addresses when ports are used, they must be
wrapped in square brackets [1]. This patch adds support for that,
using Ansible's ipwrap filter [2].

[1]: https://datatracker.ietf.org/doc/html/rfc4038#section-5.1
[2]: http://docs.ansible.com/ansible/latest/collections/ansible/utils/docsite/filters_ipaddr.html#wrapping-ipv6-addresses-in-brackets

* Do not abort other molecule jobs on failure

* Fix cache keys for Vagrant boxes

* Molecule: Derive overrides.yml location from scenario dir

# Conflicts:
#	molecule/default/molecule.yml
#	molecule/ipv6/molecule.yml

README.md

@@ -29,6 +29,7 @@ on processor architecture:
 ## ✅ System requirements
 
 - Deployment environment must have Ansible 2.4.0+.  If you need a quick primer on Ansible [you can check out my docs and setting up Ansible](https://docs.technotim.live/posts/ansible-automation/).
+  Furthermore, the [`netaddr` package](https://pypi.org/project/netaddr/) must be available to Ansible. If you have installed Ansible via apt, this is already taken care of. If you have installed Ansible via `pip`, make sure to install `netaddr` into the respective virtual environment.
 - `server` and `agent` nodes should have passwordless SSH access, if not you can supply arguments to provide credentials `--ask-pass --ask-become-pass` to each command.
 
 ## 🚀 Getting Started