[HUBZERO][#4949][COM_COURSES] fix issue where previous set unit publish_down date could be overwritten by a call to get unset unit publish_up date
[HUBZERO][#4949][COM_COURSES] fix issue where previous set unit publish_down date could be overwritten by a call to get unset unit publish_up date

anthonyfuentes/hubzero-cms,zweidner/hubzero-cms,zweidner/hubzero-cms,anthonyfuentes/hubzero-cms,zooley/hubzero-cms,anthonyfuentes/hubzero-cms,anthonyfuentes/hubzero-cms,zooley/hubzero-cms,zweidner/hubzero-cms,zweidner/hubzero-cms,zooley/hubzero-cms,zooley/hubzero-cms