Fix a small bug in cluster model
Fix a small bug in cluster model

Change-Id: Id772f6566ec415d02d4dff4ad4a8929dab36b29b

tengqm/senlin-container,Alzon/senlin,tengqm/senlin-container,stackforge/senlin,Alzon/senlin,stackforge/senlin,openstack/senlin,openstack/senlin,openstack/senlin