Tweaks to make install run idempotent

roles/nova-compute/tasks/main.yml

@@ -1,8 +1,12 @@
 # Build and install a docker image for nova-controller.
 ---
+- set_fact:
+    docker_image: webhost12.service.rug.nl/hpc/openstack-nova-compute:latest
+  tags: facts
+
 - name: pull docker image
   docker_image:
-  name: webhost12.service.rug.nl/hpc/openstack-nova-compute:latest
+    name: "{{ docker_image }}"
   tags: pull
 
 - name: install service file.

roles/nova-compute/templates/nova-compute.service

@@ -34,7 +34,7 @@ ExecStart=/usr/bin/docker run --name %n \
     -v /var/run/libvirt/libvirt-sock:/var/run/libvirt/libvirt-sock \
     -v /srv/osdisks:/var/lib/nova/instances \
     --network host \
-    hpc/openstack-nova-compute /etc/run.sh
+    {{ docker_image }} /etc/run.sh
 
 [Install]
 WantedBy=multi-user.target