Windows: Do not double increment cm_data.currentCells

During cm_cell generation the cm_data.currentCells value was
incremented twice.  As a result cm_currentCells did not equal the
number of cm_cell objects allocated.  Upon restart the AFSCache
contents would be discarded.

Change-Id: I2b62cb8268789e46f5ada4aa039e41c7ea8b47a5
Reviewed-on: http://gerrit.openafs.org/9090
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>