ofp-actions: Avoid buffer overread in BUNDLE action decoding.

Reported-at: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=9052
Signed-off-by: Ben Pfaff <blp@ovn.org>
Acked-by: Justin Pettit <jpettit@ovn.org>
format_SET_TUNNEL(const struct ofpact_tunnel *a, struct ds *s)
{
    ds_put_format(s, "%sset_tunnel%s:%s%#"PRIx64, colors.param,
                  (a->tun_id > UINT32_MAX
                   || a->ofpact.raw == NXAST_RAW_SET_TUNNEL64 ? "64" : ""),
                  colors.end, a->tun_id);
}

format_SET_TUNNEL(const struct ofpact_tunnel *a, struct ds *s)
{
    ds_put_format(s, "%sset_tunnel%s:%s%#"PRIx64, colors.param,
                  (a->tun_id > UINT32_MAX
                   || a->ofpact.raw == NXAST_RAW_SET_TUNNEL64 ? "64" : ""),
                  colors.end, a->tun_id);
}
