Add an is_running method

[mccalluc]

Refinery has this logic right now, but we should support it on our side:

    def is_running(self):
        if self.is_workflow():
            return self.analysis.running()

        try:
            self.django_docker_client.lookup_container_url(
                self.container_name
            )
            return True
        except (ExpectedPortMissing, NotFound, NoPortsOpen):
            return False

[mccalluc]

is_live is available, except it does not include NoPortsOpen, but that seems correct to me. That error would be a configuration problem, and an exception should be thrown. Keep this open until Refinery uses it.