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.

Change-Id: I29e2f3cbf45ae36c6c6b7a089d46cc6710bfbbe0
Merge "Virt driver pinning guest vCPUs to host pCPUs"