t_server_null: Test different permutations of --dh

t_server_null: Test different permutations of --dh

Do not include --dh by default, since we do not actually
need it. Use the different servers for different ways
of specifying it.

Change-Id: I480442a55025bfcce7cb68ec7564ff33b0b780e2
Signed-off-by: Frank Lichtenheld <frank@lichtenheld.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20250603142035.13685-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg31868.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>