libvirt: Bump bootstrap size (primarily for OKD)

People have been hitting space issues with OKD (FCOS)
which is 8GB by default.  Eventually I think we
should support something like simulated OpenStack instance
sizes for libvirt.

The FCOS/RHCOS difference of 8GB vs 16GB is something
I'd eventually like to fix by making RHCOS 8GB too for
consistency.

data/data/baremetal/bootstrap/main.tf

@@ -4,10 +4,19 @@ resource "libvirt_pool" "bootstrap" {
   path = "/var/lib/libvirt/openshift-images/${var.cluster_id}-bootstrap"
 }
 
+resource "libvirt_volume" "bootstrap-base" {
+  name   = "${var.cluster_id}-bootstrap-base"
+  pool   = libvirt_pool.bootstrap.name
+  source = var.image
+}
+
 resource "libvirt_volume" "bootstrap" {
   name   = "${var.cluster_id}-bootstrap"
   pool   = libvirt_pool.bootstrap.name
-  source = var.image
+  base_volume_id = libvirt_volume.bootstrap-base.id
+  # Keep this in sync with the main libvirt size in
+  # data/data/libvirt/bootstrap/main.tf
+  size = "21474836480"
 }
 
 resource "libvirt_ignition" "bootstrap" {

data/data/libvirt/bootstrap/main.tf

@@ -2,6 +2,8 @@ resource "libvirt_volume" "bootstrap" {
   name           = "${var.cluster_id}-bootstrap"
   base_volume_id = var.base_volume_id
   pool           = var.pool
+  # Bump this so it works for OKD/FCOS too
+  size = "21474836480"
 }
 
 resource "libvirt_ignition" "bootstrap" {