Windows: afslogon cast away warnings

Windows: afslogon cast away warnings

cast away size_t to int warnings in 64-bit builds.

Reviewed-on: http://gerrit.openafs.org/7634
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 76ae0f01b32d3e87273ff6d2c9c20eec59e22e16)

Change-Id: I81ba08a273aedb412642c345cd4a2762fcf1edb7
Reviewed-on: http://gerrit.openafs.org/8636
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>