dco: fix source IP selection when multihome

dco: fix source IP selection when multihome

When multihome option is enabled, OpenVPN passes ipi_addr to DCO, which
is always 0.0.0.0. It should use ipi_spec_dst instead.

Signed-off-by: Qingfang Deng <dqfext@gmail.com>
Acked-by: Antonio Quartulli <a@unstable.cc>
Message-Id: <20250227032522.3734947-1-dqfext@gmail.com>
URL: https://sourceforge.net/p/openvpn/mailman/message/59154010/
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit e4beaf7a610793f57984ec8006d26f9a695b0c74)