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
If no hostname is provided and dns_infrastructure_zone is configured
the default hostnames should use dns_infrastructure_zone instead of
domain variable
Address issues with variable interpolation within parameters for init.pp