CircleCI: update docker versions used in CI
CircleCI: update docker versions used in CI

CircleCI now has 19.03; https://circleci.com/docs/2.0/building-docker-images/#docker-version

Signed-off-by: Sebastiaan van Stijn <64b2b6d12bfe4baae7dad3d018f8cbf6b0e7a044@gone.nl>

cpuguy83/cli,thaJeztah/cli,docker/cli,cpuguy83/cli,thaJeztah/cli,docker/cli