[SPARK-20607][CORE] Add new unit tests to ShuffleSuite

## What changes were proposed in this pull request?

This PR update to two:
1.adds the new unit tests.
  testing would be performed when there is no shuffle stage,
  shuffle will not generate the data file and the index files.
2.Modify the '[SPARK-4085] rerun map stage if reduce stage cannot find its local shuffle file' unit test,
  parallelize is 1 but not is 2, Check the index file and delete.

## How was this patch tested?
The new unit test.

Author: caoxuewen <cao.xuewen@zte.com.cn>

Closes #17868 from heary-cao/ShuffleSuite.