Remove controller_preemptible option on Google Cloud

* Controller preemption is not safe or covered in documentation. Delete
the option, the variable is a holdover from old experiments
* Note, worker_preemeptible is still a great feature that's supported

google-cloud/container-linux/kubernetes/cluster.tf

@@ -11,7 +11,6 @@ module "controllers" {
   dns_zone_name = "${var.dns_zone_name}"
   machine_type  = "${var.machine_type}"
   os_image      = "${var.os_image}"
-  preemptible   = "${var.controller_preemptible}"
 
   # configuration
   networking              = "${var.networking}"

google-cloud/container-linux/kubernetes/controllers/controllers.tf

@@ -45,11 +45,6 @@ resource "google_compute_instance_template" "controller" {
     user-data = "${data.ct_config.controller_ign.rendered}"
   }
 
-  scheduling {
-    automatic_restart = "${var.preemptible ? false : true}"
-    preemptible       = "${var.preemptible}"
-  }
-
   disk {
     auto_delete  = true
     boot         = true

google-cloud/container-linux/kubernetes/controllers/variables.tf

@@ -51,12 +51,6 @@ variable "disk_size" {
   description = "The size of the disk in gigabytes."
 }
 
-variable "preemptible" {
-  type        = "string"
-  default     = "false"
-  description = "If enabled, Compute Engine will terminate instances randomly within 24 hours"
-}
-
 // configuration
 
 variable "networking" {

google-cloud/container-linux/kubernetes/variables.tf

@@ -51,12 +51,6 @@ variable "worker_count" {
   description = "Number of workers"
 }
 
-variable "controller_preemptible" {
-  type        = "string"
-  default     = "false"
-  description = "If enabled, Compute Engine will terminate controllers randomly within 24 hours"
-}
-
 variable "worker_preemptible" {
   type        = "string"
   default     = "false"