[SPARK-15537][SQL] fix dir delete issue

## What changes were proposed in this pull request?

For some of the test cases, e.g. `OrcSourceSuite`, it will create temp folders and temp files inside them. But after tests finish, the folders are not removed. This will cause lots of temp files created and space occupied, if we keep running the test cases.

The reason is dir.delete() won't work if dir is not empty. We need to recursively delete the content before deleting the folder.

## How was this patch tested?

Manually checked the temp folder to make sure the temp files were deleted.

Author: Bo Meng <mengbo@hotmail.com>

Closes #13304 from bomeng/SPARK-15537.