Add missing parameter to Model Manager cluster

Change-Id: I9829e21a2ba7ec3f53d6051d7f248bd60e6c8090
diff --git a/classes/cluster/model_manager/model_manager/init.yml b/classes/cluster/model_manager/model_manager/init.yml
index 0e5dded..781d1f4 100644
--- a/classes/cluster/model_manager/model_manager/init.yml
+++ b/classes/cluster/model_manager/model_manager/init.yml
@@ -14,6 +14,7 @@
     # identity params
     openstack_region: RegionOne
     admin_email: root@localhost
+    openstack_version: mitaka
     keystone_version: mitaka
     keystone_service_token: qzWYJmNiiXYRSipdWda0
     rabbitmq_openstack_password: workshop