Windows: NPLogonNotify secure erase password

Windows: NPLogonNotify secure erase password

The user's password is copied during the NPLogonNotify
processing, be sure to erase it from the stack before the
function completes.

Reviewed-on: http://gerrit.openafs.org/7632
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>
(cherry picked from commit 187af8d11350c2ff509244f216c72bdd4b88451a)

Change-Id: I40f52324067597e4eb96bfd7ed19f18e154ef8ee
Reviewed-on: http://gerrit.openafs.org/8632
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>