dco-freebsd: fix peer stats storage on client instances

dco-freebsd: fix peer stats storage on client instances

Commit bf01a96 introduced a bug in the dco-freebsd path by attempting to
store peer statistics in a structure that only exists on server
instances. This leads to a SIGSEGV on non-server instances due to a NULL
multi_context pointer.

Resolve this by checking what mode the current instance is running in
and storing peer stats accordingly.

Fixes: https://github.com/OpenVPN/openvpn/issues/875
Change-Id: I92b5f3996f2a2180fa5e94719603078c1fc2f7f6
Signed-off-by: Ralf Lici <ralf@mandelbit.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Gerrit URL: https://gerrit.openvpn.net/c/openvpn/+/1290
Message-Id: <20251028113310.19921-1-gert@greenie.muc.de>
Signed-off-by: Gert Doering <gert@greenie.muc.de>