[libvirt] [RFC v2][remote]

Hello. I'll reword the previous letter. In libvirt we have connection close callback for drivers that have persistent internal connection to notify client that this connection is closed. Vz driver has internal persistent connection so I wanted to add support of this callback to vz driver. Now clients with connections urls like 'vz:///system' are notified of connection close event. But if connection url is like 'vz+<transport>://system we have a remote driver between client and vz driver and client is not notified as remote driver doesn't handle this event. The problem is that remote driver can't just relay this event as domain one as there is no means to do it in driver interface. The quick fix is to close the connection between daemon and remote driver from daemon side is case of close event. This will trigger connection close event in remote driver and client finally will be notified. I doubt this is a good approach as it looks like we forced to take specific action of closing connection to daemon only due to lack of appropriate driver interface. So the proposition is to move connection close event registration/deregistration/notifying to driver level so remote driver could relay them just like say domain events.