Allow specification of libvirt guest interface backend driver
Allow specification of libvirt guest interface backend driver

Extend the libvirt config APIs to allow the backend driver name
to be set for guest interface devices

Change-Id: Ibde6f0c5e1700b414bb188fb47f511a47cfc0abf
Signed-off-by: Daniel P. Berrange <bb938cf255e055ff3507f2627d214e8e62118fcf@redhat.com>

n0ano/gantt,n0ano/gantt