[SPARK-17276][CORE][TEST] Stop env params output on Jenkins job page

https://issues.apache.org/jira/browse/SPARK-17276

## What changes were proposed in this pull request?

When trying to find error msg in a failed Jenkins build job, I'm annoyed by the huge env output.
The env parameter output should be muted.

![screen shot 2016-08-26 at 10 52 07 pm](https://cloud.githubusercontent.com/assets/3925641/18025581/b8d567ba-6be2-11e6-9eeb-6aec223f1730.png)

## How was this patch tested?

Tested manually on local laptop.

Author: Xin Ren <iamshrek@126.com>

Closes #14848 from keypointt/SPARK-17276.