Windows: Track AuthGroup in Context Control Block

Windows: Track AuthGroup in Context Control Block

Tracking the AuthGroup in the File Control Block proved to be
insufficient to ensure that dirty extents can be stored back
to the file server when an anti-virus service opens a file
in authgroup without 'write' permission immediate after the
application performing a WriteFile() opens it.  In this situation
the Fcb ends up with the AuthGroup set to the anti-virus value
and not the one that belongs to the writing application.

Tracking the AuthGroup by Ccb provides the ability to select
an AuthGroup from the list of open handles instead of tracking
the most recent one.

Change-Id: I851ea646feb531d7c765e1cf789a4ba541e4a150
Reviewed-on: http://gerrit.openafs.org/6333
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@secure-endpoints.com>
Tested-by: Jeffrey Altman <jaltman@secure-endpoints.com>