run-tests: define cleanup() on unittest class

We need a cleanup() on our unittest TestCase class to conform with the
execution API. This will eventually be replaced by tearDown().

tests/run-tests.py

@@ -1340,6 +1340,10 b' class TestRunner(object):'
                 else:
                     self.fail('Unknown test result code: %s' % code)
 
+            # We need this proxy until tearDown() is implemented.
+            def cleanup(self):
+                return t.cleanup()
+
         return MercurialTest(test)
 
     def _cleanup(self):