Support SR-IOV networking in libvirt

This patch takes care of changing the libvirt modules in support of SR-IOV
networking. Added full support in configuring the two VIF types:
VIF_TYPE_802QBH and VIF_TYPE_HW_VEB and in generating the corresponding
domain XML. It also adds support of attaching/detaching SR-IOV ports
on instance suspend/snapshot/resume operations.

Change-Id: Ibc47d13f47fa0b41cefc27bfff942cdbba6eb399
Implements: blueprint pci-passthrough-sriov
Merge "Support SR-IOV networking in libvirt"