Windows: buffer DV ranges do not work for directories

Windows: buffer DV ranges do not work for directories

In cm_MergeStatus, always set cm_scache_t.bufDataVersionLow
to the new data version because the cm_dir package does not
support version ranges.   All modified dir buffers have their
dataVersion field set to the current data version value.

Failure to update the bufDataVersionLow field can result in
B+ Trees being constructed from out of date directory information.

Change-Id: Ic6bb6f78275de9c6c7960f2fc7c06c507b1144c1
Reviewed-on: http://gerrit.openafs.org/6649
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@secure-endpoints.com>
Tested-by: Jeffrey Altman <jaltman@secure-endpoints.com>