Windows: SetVolumeState is not an invalidation

Windows: SetVolumeState is not an invalidation

Volume state notifications (online, offline, unknown) from the
afsd_service.exe to the afs redirector are not invalidation
events.  The verify flag should not be set, the extents should
not be purged, etc.  Just set or clear the AFS_VOLUME_FLAGS_OFFLINE.

Change-Id: I046468e614c836981db228aa142d2c8bdb03a9ad
Reviewed-on: http://gerrit.openafs.org/8651
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>