Fix VM base images being overwritten

The base image is used as backing image for the VM images, so
overwriting it results in corrupt data after VM reboots.

site-cookbooks/kosmos_kvm/recipes/host.rb

@@ -12,17 +12,19 @@ directory "/var/lib/libvirt/images/base" do
   mode "0750"
 end
 
-# Base Ubuntu 20.04 image
-remote_file "/var/lib/libvirt/images/base/ubuntu-20.04-server-cloudimg-amd64-disk-kvm.qcow2" do
-  source "http://cloud-images.ubuntu.com/releases/focal/release/ubuntu-20.04-server-cloudimg-amd64-disk-kvm.img"
+# Base VM image
+remote_file node["kosmos_kvm"]["host"]["qemu_base_image"]["path"] do
+  source node["kosmos_kvm"]["host"]["qemu_base_image"]["url"]
+  checksum node["kosmos_kvm"]["host"]["qemu_base_image"]["checksum"]
   owner "libvirt-qemu"
   group "kvm"
   mode "0640"
 end
 
-cookbook_file "/usr/local/sbin/create_vm" do
-  source "create_vm"
+template "/usr/local/sbin/create_vm" do
+  source "create_vm.erb"
   mode "0750"
+  variables base_image_path: node["kosmos_kvm"]["host"]["qemu_base_image"]["path"]
 end
 
 firewall_rule 'ssh-alt-port' do