Virt driver pinning guest vCPUs to host pCPUs

This feature aims to improve the libvirt driver so that it is
able to strictly pin guest vCPUS to host pCPUs. This provides
the concept of "dedicated CPU" guest instances.

Previously approved: juno
Change-Id: I73903460f552b50fd4f333f862d14baed83e5fab
Merge "Virt driver pinning guest vCPUs to host pCPUs"