This reverts commit 7be5fe66.

This commit broke resctrl, because it missed the fact that the
virResctrlInfoGetCache() has side-effects causing it to actually
change the virResctrlInfo parameter, not merely get data from
it.

This code will need some refactoring before we can try separating
it from virCapabilities again.
Reviewed-by: NCole Robinson <crobinso@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>