Add optional cluster_domain_suffix variable

* Allow kube-dns to respond to DNS queries with a custom
suffix, instead of the default 'cluster.local'
* Useful when multiple clusters exist on the same local
network and wish to query services on one another

bare-metal/container-linux/pxe-worker/cl/bootkube-worker.yaml.tmpl

@@ -58,7 +58,7 @@ systemd:
           --anonymous-auth=false \
           --client-ca-file=/etc/kubernetes/ca.crt \
           --cluster_dns={{.k8s_dns_service_ip}} \
-          --cluster_domain=cluster.local \
+          --cluster_domain={{.cluster_domain_suffix}} \
           --cni-conf-dir=/etc/kubernetes/cni/net.d \
           --exit-on-lock-contention \
           --hostname-override={{.domain_name}} \

bare-metal/container-linux/pxe-worker/groups.tf

@@ -13,9 +13,10 @@ resource "matchbox_group" "workers" {
     etcd_endpoints = "${join(",", formatlist("%s:2379", var.controller_domains))}"
 
     # TODO
-    etcd_on_host        = "true"
-    k8s_etcd_service_ip = "10.3.0.15"
-    k8s_dns_service_ip  = "${var.kube_dns_service_ip}"
-    ssh_authorized_key  = "${var.ssh_authorized_key}"
+    etcd_on_host          = "true"
+    k8s_etcd_service_ip   = "10.3.0.15"
+    k8s_dns_service_ip    = "${var.kube_dns_service_ip}"
+    cluster_domain_suffix = "${var.cluster_domain_suffix}"
+    ssh_authorized_key    = "${var.ssh_authorized_key}"
   }
 }

bare-metal/container-linux/pxe-worker/variables.tf

@@ -64,3 +64,9 @@ variable "kernel_args" {
     "root=/dev/sda1",
   ]
 }
+
+variable "cluster_domain_suffix" {
+  description = "Queries for domains with the suffix will be answered by kube-dns. Default is cluster.local (e.g. foo.default.svc.cluster.local) "
+  type        = "string"
+  default     = "cluster.local"
+}