Reworked cluster_add_nodes and cluster_del_nodes
Reworked cluster_add_nodes and cluster_del_nodes

There could still be contention condition in node level because we are
not yet locking them...

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