resurrect test_handle_superevent

The test_handle_superevent was xfailed. The celery issue: https://github.com/celery/celery/issues/4405 is not closed yet (reason for the xfail). However, the tests can be run without a live worker. This is an important test and should be resurrected. I have done a first pass, sometimes patching high-level functions in the orchestrator since parts of our canvas is now more complex. However these test will eventually need to be made more robust.