[COPS-3443] Make default docker image the one in resource.json

[elezar]

Specifying the default docker image twice means that the default installation doesn't work on local universes.

This change removes the default from config.json which makes the value specified in resource.json the default. This does not change behaviour, but makes it easier to use Spark from a local universe.

The alternative would be extensive documentation changes.

[mpereira]

Is {{ docker-image }} in resource.json interpolated to a value that is compatible with local universes?

[elezar]

Is {{ docker-image }} in resource.json interpolated to a value that is compatible with local universes?

For the versions we release, this is mesosphere/spark (see: https://github.com/mesosphere/universe/blob/version-3.x/repo/packages/S/spark/200/resource.json#L5) and is populated at build time. The difference is that when building a local universe certain URIs and containers are updated in the resource.json and these are used instead.

[mpereira]

Gotcha.

[samvantran]

Looks good to me !