Allow --dhcp-option in config file when windows-driver is wintun

Allow --dhcp-option in config file when windows-driver is wintun

When wintun is in use we mutate ip_win32_type to NETSH
and then complain that ip-win32 option should be dynamic or adaptive
if any --dhcp-option directive is present in the config file. This
causes a fatal error.

How to reproduce: specify a --dhcp-option in the config and change the
--windows-driver to wintun.

Fix this behaviour. A typo in the message is also corrected.

Signed-off-by: Selva Nair <selva.nair@gmail.com>
Acked-by: Lev Stipakov <lstipakov@gmail.com>
Message-Id: <1600126181-16364-1-git-send-email-selva.nair@gmail.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg21005.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit b8625abbd5be21a810b648058e6e411a7ff19702)