data/libvirt: Resize to 16 GiB

This is the size of the current RHCOS images:

  $ qemu-img info ~/.cache/openshift-install/libvirt/image/2454fcdc0a61a9005fbf916b54fbe332
  image: /home/trking/.cache/openshift-install/libvirt/image/2454fcdc0a61a9005fbf916b54fbe332
  file format: qcow2
  virtual size: 16G (17179869184 bytes)
  disk size: 1.6G
  cluster_size: 65536
  Format specific information:
      compat: 1.1
      lazy refcounts: false
      refcount bits: 16
      corrupt: false

Resizing here will allow the OS folks to stop guessing which size we
need [1,2].  And when we need future resizes, we can update here
instead of bugging the OS team.

Also inline the volume in the libvirt Terraform module.  The
libvirt/volume module indirection was unnecessary indirection.

[1]: #126
[2]: openshift/os#228

data/data/libvirt/main.tf

@@ -2,17 +2,17 @@ provider "libvirt" {
   uri = "${var.tectonic_libvirt_uri}"
 }
 
-module "libvirt_base_volume" {
-  source = "./volume"
-
-  image = "${var.tectonic_os_image}"
+resource "libvirt_volume" "base" {
+  name   = "coreos_base"
+  source = "${var.tectonic_os_image}"
+  size   = 17179869184
 }
 
 module "bootstrap" {
   source = "./bootstrap"
 
   addresses      = ["${var.tectonic_libvirt_bootstrap_ip}"]
-  base_volume_id = "${module.libvirt_base_volume.coreos_base_volume_id}"
+  base_volume_id = "${libvirt_volume.base.id}"
   cluster_name   = "${var.tectonic_cluster_name}"
   ignition       = "${var.ignition_bootstrap}"
   network_id     = "${libvirt_network.tectonic_net.id}"
@@ -21,7 +21,7 @@ module "bootstrap" {
 resource "libvirt_volume" "master" {
   count          = "${var.tectonic_master_count}"
   name           = "master${count.index}"
-  base_volume_id = "${module.libvirt_base_volume.coreos_base_volume_id}"
+  base_volume_id = "${libvirt_volume.base.id}"
 }
 
 resource "libvirt_ignition" "master" {