hack/terraform-quickstart: default root disk size to 30GB

This matches the defaults in tectonic-installer and it means we don't
run out of disk space building conformance tests on a node.

Author: Patrick Baxter

hack/terraform-quickstart/main.tf

@@ -13,6 +13,10 @@ resource "aws_instance" "bootstrap_node" {
   tags {
     Name = "${var.instance_tags}"
   }
+  root_block_device {
+    volume_type = "gp2"
+    volume_size = "30"
+  }
 }
 
 resource "aws_instance" "worker_node" {
@@ -25,6 +29,11 @@ resource "aws_instance" "worker_node" {
   tags {
     Name = "${var.instance_tags}"
   }
+
+  root_block_device {
+    volume_type = "gp2"
+    volume_size = "30"
+  }
 }
 
 resource "aws_instance" "master_node" {
@@ -37,6 +46,11 @@ resource "aws_instance" "master_node" {
   tags {
     Name = "${var.instance_tags}"
   }
+
+  root_block_device {
+    volume_type = "gp2"
+    volume_size = "30"
+  }
 }
 
 data "aws_ami" "coreos_ami" {