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

.ansible-lint

@@ -9,8 +9,9 @@ exclude_paths:
   # The "converge" and "reset" playbooks use import_playbook in
   # conjunction with the "env" lookup plugin, which lets the
   # syntax check of ansible-lint fail.
-  - '**/converge.yml'
-  - '**/reset.yml'
+  - 'molecule/**/converge.yml'
+  - 'molecule/**/prepare.yml'
+  - 'molecule/**/reset.yml'
 
 skip_list:
   - 'fqcn-builtins'