stop leaking tempdirs

test_wrappers built temp dirs for running tests, but never
cleaned them up. So your /tmp is very full of tempest code now.

Fix this with an add cleanup

Change-Id: I4c05ba16c524b844f3cf43cfe0969ddd20238486

tempest/tests/test_wrappers.py

@@ -27,6 +27,7 @@ class TestWrappers(base.TestCase):
         super(TestWrappers, self).setUp()
         # Setup test dirs
         self.directory = tempfile.mkdtemp(prefix='tempest-unit')
+        self.addCleanup(shutil.rmtree, self.directory)
         self.test_dir = os.path.join(self.directory, 'tests')
         os.mkdir(self.test_dir)
         # Setup Test files