tun.c: reorder IPv6 ifconfig on Windows

tun.c: reorder IPv6 ifconfig on Windows

The IPv6 interface network route should be setup as soon as possible
after the interface address is set. Actually, all routes should be added
before DNS servers are configured. This would allow Windows to validate
DNS servers properly instead of shutting the validation off.

The cleanup order has been changed to match reverse order of ifconfig.
An additional check was added to skip the cleanup when --ip-win32 is set
to manual.

Signed-off-by: Simon Rozman <simon@rozman.si>
Acked-by: Lev Stipakov <lstipakov@gmail.com>
Message-Id: <20200310094822.588-1-simon@rozman.si>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg19541.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>