Use the return value of visit_check_struct() and visit_check_list()
for error checking instead of local_err. This allows to get rid of
the error propagation overhead.

Signed-off-by: Greg Kurz <groug@kaod.org>
Message-Id: <20200914123505.612812-10-groug@kaod.org>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>