So far, libvirt generates the following path for hugepages:

  $mnt/libvirt/qemu/$id-$shortName

where $mnt is the mount point of hugetlbfs corresponding to
hugepages of desired size (e.g. /dev/hugepages), $id is domain ID
and $shortName is shortened version of domain name. So for
instance, the generated path may look something like this:

  /dev/hugepages/libvirt/qemu/1-QEMUGuest

But this won't work with embed driver really, because if there
are two instances of embed driver, and they both want to start a
domain with the same name and with hugepages, both drivers will
generate the same path which is not desired. Fortunately, we can
reuse the approach for machined name generation
(v6.1.0-178-gc9bd08ee) and include part of hash of the root in
the generated path.

Note, the important change is in qemuGetBaseHugepagePath(). The
rest is needed to pass driver around.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NAndrea Bolognani <abologna@redhat.com>
Reviewed-by: NDaniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>