qcow2: Reuse refcount table in calculate_refcounts() We will later call calculate_refcounts multiple times, so reuse the refcount table if possible. Signed-off-by: Max Reitz <mreitz@redhat.com> Reviewed-by: BenoƮt Canet <benoit.canet@nodalink.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>