Allow setting custom PXE boot kernel_args on bare-metal

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

@@ -8,12 +8,11 @@ resource "matchbox_profile" "bootkube-worker-pxe" {
   ]
 
   args = [
-    "root=/dev/sda1",
     "coreos.config.url=${var.matchbox_http_endpoint}/ignition?uuid=$${uuid}&mac=$${mac:hexhyp}",
     "coreos.first_boot=yes",
     "console=tty0",
     "console=ttyS0",
-    "kvm-intel.nested=1",
+    "${var.kernel_args}",
   ]
 
   container_linux_config = "${file("${path.module}/cl/bootkube-worker.yaml.tmpl")}"

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

@@ -53,3 +53,14 @@ variable "kube_dns_service_ip" {
   type        = "string"
   default     = "10.3.0.10"
 }
+
+# optional
+
+variable "kernel_args" {
+  description = "Additional kernel arguments the server should boot with."
+  type        = "list"
+
+  default = [
+    "root=/dev/sda1",
+  ]
+}