Disable DCO if proxy is set via management

Disable DCO if proxy is set via management

Commit

    45a1cb2a ("Disable DCO if proxy is set via management")

attempted to disable DCO when proxy is set via management interface. However,
at least on Windows this doesn't work, since:

 - setting tuntap_options->disable_dco to true is not enough to disable DCO
 - at this point it is a bit too late, since we've already done DCO-specific
   adjustments

Since proxy can be set via management only if --management-query-proxy is
specified, the better way is to add a check to dco_check_startup_option().

Github: fixes OpenVPN/openvpn#522

Change-Id: I16d6a9fefa317d7d4a195e786618328445bdbca8
Signed-off-by: Lev Stipakov <lev@openvpn.net>
Acked-by: Frank Lichtenheld <frank@lichtenheld.com>
Message-Id: <20240318181744.20625-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg28415.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit fd6b8395f6cee8a61111c28f335ec25ed6db11f7)