Add swarm job for migrations

[chris34]

• documentation seems to be only in PR → https://github.com/docker/docker.github.io/pull/12037/files
• Add support for swarm jobs moby/moby#40307, Add jobs support to CLI docker/cli#2262, Added Swarm Job support to Stack Deploy docker/cli#2907

[chris34]

Migration is now executed on every deployment done with Ansible. Thus, someone can not forget about it. And we do not need to add a swarm job.

I would not run it on every startup (expect for development.)