Correct error text when no Windows TAP device is present

Starting with the 2.3-series, the TAP-Windows driver/utilities and
OpenVPN are separately installed components. The error message given to
users without available TAP devices uses the pre-2.3 path that does not
exist. The path should be listed under the TAP-Windows program group
that the tap-windows project installer uses.

Resolves bug #320

Signed-off-by: Josh Cepek <josh.cepek@usa.net>
Acked-by: David Sommerseth <dazo@users.sourceforge.net>
Message-Id: <kv4ece$s8s$1@ger.gmane.org>
URL: http://article.gmane.org/gmane.network.openvpn.devel/7825
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit 2d34628af995676c8ecddb953897c334b96a6a6b)