Add Parallels Cloud Server support into virt/libvirt driver

This specification proposes to implement modification in
virt/libvirt driver to support Parallels Cloud Server
(http://www.parallels.com/products/pcs/).

blueprint pcs-support
Change-Id: Ibbc19ca2181827e7c6576f82f756898a13503f2e
Merge "Add Parallels Cloud Server support into virt/libvirt driver"