Add libguestfs-tools package to nova utilities

Include libguestfs-tools package as part of nova
utilities class and update spec tests. This
package provides library and tools for managing
virtual disks such as guestmount which are useful
for nova-compute.

Change-Id: Ie63b1417b5d9f584a23baa52f26efc3ff71b8785
(cherry picked from commit 79f7f3be016c172ee6bca30eb72d9546049efcf2 )