Minor tweaking to placement policy
Minor tweaking to placement policy

The placement policy should make a decision during 'pre_op', not when
enforced.

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