Further down the rabbit hole. ;)

tasks/persistent_cloud.yml

@@ -55,13 +55,14 @@
   changed_when: volume_available.rc == 0
   ignore_errors: True
   when: volumes is defined
+  always_run: True
 
 #
 # If it is attach it.
 #
 - local_action: shell nova --os-auth-url="{{os_auth_url}}" --os-username="admin" --os-password="{{ADMIN_PASS}}" --os-tenant-name={{inventory_tenant}} volume-attach "{{inventory_instance_name}}" "{{item.volume_id}}" "{{item.device}}"
   with_items: "{{volumes}}"
-  when: volume_available.rc == 0
+  when: volumes is defined and volume_available is defined and volume_available.rc == 0
 
 - name: wait for he host to be hot
   local_action: wait_for host={{ public_ip }} port=22 delay=1 timeout=600