Grid 4 has the ability to start Docker containers on-demand, this means that it starts a Docker container in the background for each new session request, the test gets executed there, and when the test completes, the container gets thrown away. This execution mode can be used either in the Standalone or Node roles. The "dynamic" execution mode needs to be told what Docker images to use when the containers get started. Additionally, the Grid needs to know the URI of the Docker daemon. If you...