Re: [libvirt] [PATCH 1/2] Restructure domain struct interface "driver" data for easier expansion

When the <driver> element (and its "name" attribute) was added to the domain XML's interface element, a "backend" enum was simply added to the toplevel of the virDomainNetDef struct.

This patch changes virDomainNetDef in two ways:

1) Rename the item in the struct from "backend" to "name", so that it's the same in the XML and in the struct, hopefully avoiding confusion for someone unfamiliar with the function of the attribute. 2) Create a "driver" union within virDomainNetDef, and a "virtio" struct in that struct, which contains the "name" enum value. 3) Move around the virDomainNetParse and virDomainNetFormat functions to allow for simple plugin of new attributes without disturbing existing code. (you'll note that this results in a seemingly redundant if() in the format function, but that will no longer be the case as soon as a 2nd attribute is added).