Support of DNS domain for DHCP-less drivers

Support of DNS domain for DHCP-less drivers

We set DNS domain either via interactve service or DHCP.
When interactive service is not used, for example,
when profiles are started by OpenVPNService, this option
is not working for DCO and wintun.

This implements setting DNS domain via WMIC command,
similar to implementation in interactive service.
This is done when:

 - interactive service is not used

 - DHCP is not used (ip-win32 is either NETSH or IPAPI,
   or IPv4 address is not pushed)

Github: fixes OpenVPN/openvpn#306

Change-Id: Ic72a4ecd0414c0d7bf013415f52640fd122cb739
Signed-off-by: Lev Stipakov <lev@openvpn.net>
Acked-by: Selva Nair <selva.nair@gmail.com>
Message-Id: <20230406071546.1056-1-lstipakov@gmail.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg26582.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>