caps: Do not memoize CPU topology

This patch prevents the CPU topology from being memoized, this is
needed in order to support host CPU hotplugging, to avoid using
disabled logical CPUs and to rescan for topology changes in ppc64.

Change-Id: Ia0e87b50d4fe882240c93a0a1600e3a0cb98d443
Signed-off-by: Vitor de Lima <vdelima@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/34189
Reviewed-by: Dan Kenigsberg <danken@redhat.com>