Implement step function terminate

[martinbattentive]

I was looking for a way to stop a running step function and ran across this TODO in metaflow/plugins/aws/step_functions/step_functions_client.py:

def terminate_execution(self, state_machine_arn, execution_arn):
    # TODO
    pass

Any chance of this getting implemented in the near future?

[mikesteroonie]

I tried implementing this in pr #1596. Are you running into loop behavior as of now? Or do you need to shut down the instance to stop the step function?

[madhur-ob]

Done by #1695