quick fix for 2539 (#2603)
quick fix for 2539 (#2603)

* fix for issue #2539
* add if clauses to avoid repeating adding exisiting environment variables



intel-analytics/BigDL,intel-analytics/BigDL,yangw1234/BigDL,yangw1234/BigDL,intel-analytics/BigDL,yangw1234/BigDL,yangw1234/BigDL,intel-analytics/BigDL