Multiple bug fixes for register_dns

- Bug 1162093 - infrastructure dns improvements
    - https://bugzilla.redhat.com/show_bug.cgi?id=1162093
    - include the dns_infrastructure_key in oo_instrastructure.conf
    - Allow changes to oo_infrastructure.conf file
    - No longer reference fqdn fact in register_dns
- Add comments to templates stating that they are managed by puppet
- Bug 1162901 - ensure correct dns key algo used
    - https://bugzilla.redhat.com/show_bug.cgi?id=1162901
    - Previously register_dns.pp used pick to choose between
      bind_key_algorithm and dns_infrastructure_key_algorithm, but since
      they both had default values of HMAC-MD5,
      dns_infrastructure_key_algorithm was always used.
- Bug 1162454 - default hostnames should use infra zone if provided
    - https://bugzilla.redhat.com/show_bug.cgi?id=1162454
    - If no hostname is provided and dns_infrastructure_zone is configured
      the default hostnames should use dns_infrastructure_zone instead of
      domain variable

Does this properly work? I'd really write some tests for this because this feels like it could break easily and not do what you'd expect it to do.