Add tracking of control net mac addresses in the node_history.
For InstaGeni, need to record and be able to search for history by control net mac address. We now record this in the node_history table, with corresponding change to the ShowNodeHistory web page. The backend changes required are that we 1) actually generate a mac address for VMs and stick it into the interfaces record, 2) return that mac from tmcd in the jailconfig, and 3) have the openvz library create the control net interface using that mac. On the openvz image, needed to switch to using a control network bridge for all interfaces (not just routable ones) so that traffic leaves the node with the correct mac.