t_server_null: persist test log files

t_server_null: persist test log files

The goal is to help debug issues with t_server_null. The immediate goal
is to be able to debug server startup issues encountered on some of the
*BSD platforms.

Change-Id: I49f1e7d25edb62bf202ffceb45dedc213f2eafdd
Signed-off-by: Samuli Seppänen <samuli.seppanen@gmail.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20241024133220.4864-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/search?l=mid&q=20241024133220.4864-1-gert@greenie.muc.de
URL: https://gerrit.openvpn.net/c/openvpn/+/776
Signed-off-by: Gert Doering <gert@greenie.muc.de>