Virt driver guest vCPU topology configuration

This feature aims to give users and administrators the ability to
control the vCPU topology exposed to guests. This enables them to
avoid any of the limitations on vCPU topologies that OS vendors
place on their projects.

Change-Id: I029c98763abedd732c3ea0396dd281bf592ab64a
Merge "Virt driver guest vCPU topology configuration"