iservice: use interface index with netsh

iservice: use interface index with netsh

We use the interface index with netsh everywhere else, so convert this
invocation of netsh to index use as well.

Remove CmpWString() as it is no longer used anywhere.

Change-Id: I329b407693b97dd048bd3788ecad345d6e25dab2
Signed-off-by: Heiko Hund <heiko@ist.eigentlich.net>
Acked-by: Lev Stipakov <lstipakov@gmail.com>
Gerrit URL: https://gerrit.openvpn.net/c/openvpn/+/1308
Message-Id: <20251030150214.4161-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg34037.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>