Fixes cinder backend support for backends without a volume_group key

Currently we allow multiple cinder backends to be configured. Some
do not need a volume_group defined. This patch fixes the logic around
when we add a volume group device to cinder (only when defined)

Change-Id: I118546e8bc6c3fa7fac62b96ea2295a76711e0f3
Closes-Bug: 1439843

playbooks/os-cinder-install.yml

@@ -20,11 +20,15 @@
   pre_tasks:
     - name: Add volume group block device to cinder
       shell: |
+        {% if item.1.volume_group is defined %}
         if [ "$(pvdisplay | grep -B1 {{ item.1.volume_group }} | awk '/PV/ {print $3}')" ];then
           for device in `pvdisplay | grep -B1 {{ item.1.volume_group }} | awk '/PV/ {print $3}'`
             do lxc-device -n {{ container_name }} add $device
           done
         fi
+        {% else %}
+        echo "{{ item.1 }} volume_group not defined"
+        {% endif %}
       with_items: cinder_backends|dictsort
       when: >
         cinder_backends is defined and