Properly unmap ring buffer file-map in interactive service

Properly unmap ring buffer file-map in interactive service

The return value of MapViewOfFile must be passed to UnmapViewofFile,
instead of the file handle.

Github: Fixes OpenVPN/openvpn#206

v2: move *ring = NULL inside if {}

Signed-off-by: Selva Nair <selva.nair@gmail.com>
Acked-by: Lev Stipakov <lstipakov@gmail.com>
Message-Id: <20221229134729.1474034-1-selva.nair@gmail.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg25859.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>