message: Fix flaky test by increasing sleep timer
diff: @@ -237,7 +237,7 @@ class MapDefunTest(test_base.DatasetTestBase):
  thread = self.checkedThread(
  self._assert_op_cancelled, args=(sess, map_defun_op))
  thread.start()
  - time.sleep(0.1)
  + time.sleep(0.2)
  sess.close()
  thread.join()
  