Remove link_mtu parameter when running up/down scripts

Remove link_mtu parameter when running up/down scripts

The link mtu is no longer used and calculating a compatibility link
MTU just for scripts makes little sense as well. Replace the parameter
instead with a fixed parameter 0.

Signed-off-by: Arne Schwabe <arne@rfc2549.org>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20220101162532.2251835-9-arne@rfc2549.org>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg23493.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>