document swarm docker version more clearly

[jodh-intel]

We currently document that docker 1.12 is required for using swarm in the versions database:

• https://github.com/kata-containers/runtime/blob/master/versions.yaml#L100..L106

However, that's not strictly true since "basic" swarm works:

• tests: Add initial swarm tests tests#199

We need to update the versions database to clarify that somehow. I vote for adding a reference to the issue in question using a new swarm-issue value like this:

  docker:
    description: "Moby project container manager"
    notes: "Docker Swarm requires an older version of Docker."
    url: "https://github.com/moby/moby"
    version: "v17.12-ce"
    meta:
      swarm-version: "1.12.1"
      swarm-issue: "https://github.com/kata-containers/runtime/issues/175"

[GabyCT]

@jodh-intel, I have a question regarding this issue, it is possible to launch Swarm replicas with Docker 17.12.1, however, it is not possible to ping among the replicas mainly because of issue #175. The tests that were added check basics like interface names (#175). By using the version 1.12.1 is possible to ping among the replicas and do more complex stuff. Should I change the versions.yaml with docker 17.12.1? Thanks for everything.

[GabyCT]

Closing this issue as we make a reference about which version is working with swarm https://github.com/kata-containers/runtime/blob/master/versions.yaml#L209, also we specify in the Limitations about swarm testing https://github.com/kata-containers/documentation/blob/master/Limitations.md