docker manager crashes if unknown containers have tag rc2.live

[mlilback]

A fatalError happens if there are unknown tags. This will only happen when the docker image info has added/removed containers, which should be incredibly rare.

[mlilback]

also happens if you rename a container to keep it around for debugging. The problem is in DockerContainer.init(json:). Exceptions are thrown, and there is no easy way to fix this right now. Probably best to fix when changing to swift serialization. DockerAPIImplementation.parseContainers(json:) needs to use a flatMap and ignore any containters that aren't properly deserialized.