bind real nodes to cn_node_lease instead of cn_node
Eventually, when we add VMCreate() in the API, it will create a cn_node and return a capability, but the actual VM will be lazily created only when node.reset() is invoked. Thus VM openstack UUIDs are only ever associated with cn_node_lease objects. Further, when node.reset() is called, the current VM is destroyed, and a new one created.