Allow MTU for bare-metal Calico to be customized

* Calico on bare-metal defaults to IP-in-IP encapsulation and MTU 1480

bare-metal/container-linux/kubernetes/bootkube.tf

@@ -1,12 +1,13 @@
 # Self-hosted Kubernetes assets (kubeconfig, manifests)
 module "bootkube" {
-  source = "git::https://github.com/poseidon/bootkube-terraform.git?ref=a52f99e8cc8b395cf2b28f74a9f79c01b63e99ae"
+  source = "git::https://github.com/poseidon/bootkube-terraform.git?ref=5ffbfec46dc05721eaf9d15c3c9bbedefaead1bc"
 
   cluster_name                  = "${var.cluster_name}"
   api_servers                   = ["${var.k8s_domain_name}"]
   etcd_servers                  = ["${var.controller_domains}"]
   asset_dir                     = "${var.asset_dir}"
   networking                    = "${var.networking}"
+  network_mtu                   = "${var.network_mtu}"
   pod_cidr                      = "${var.pod_cidr}"
   service_cidr                  = "${var.service_cidr}"
   experimental_self_hosted_etcd = "${var.experimental_self_hosted_etcd}"

bare-metal/container-linux/kubernetes/variables.tf

@@ -68,6 +68,12 @@ variable "networking" {
   default     = "flannel"
 }
 
+variable "network_mtu" {
+  description = "CNI interface MTU (applies to calico only)"
+  type        = "string"
+  default     = "1480"
+}
+
 variable "pod_cidr" {
   description = "CIDR IP range to assign Kubernetes pods"
   type        = "string"