In Python land, the method run once a test method runs is called tearDown(),
not cleanUp(). In other words, the existing methods were never called and we
were always leaving lots of "gstools_test*" directories in /tmp.

Change-Id: Ib1de95c7ba92922b98571780f389237de0dcb253
Reviewed-on: https://chromium-review.googlesource.com/753383
Commit-Queue: Aaron Gable <agable@chromium.org>
Reviewed-by: Aaron Gable <agable@chromium.org>