Skip DNS address validation

Skip DNS address validation

When adding IPv4 DNS servers without interactive service use
"validate=no", on Windows 7 and higher, to skip time consuming automatic
address validation, that is on by default.

Fix uses adapted code from commit 786e06a

Signed-off-by: Domagoj Pensa <domagoj@pensa.hr>
Acked-by: Lev Stipakov <lstipakov@gmail.com>
Acked-by: Selva Nair <selva.nair@gmail.com>
Message-Id: <20200205124615.15758-2-domagoj@pensa.hr>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg19355.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>