* Calico on GCE with IP-in-IP encapsulation and MTU 1440
* Calico on DO with IP-in-IP encapsulation and MTU 1440
* Digital Ocean firewalls don't support IPIP protocol yet
* Remove k8s_domain_name input variable, the controller DNS
record will be "${var.cluster_name}.${dns_zone}"
* Rename dns_base_zone to dns_zone
* Rename dns_base_zone_name to dns_zone_name