One use case of spawning containers from a task is to set up some kind of text fixture. The container will expose some port to the task. We should provide a way (e.g., a boolean in host.create) to indicate that we should set up a mapping between a container port and the underlying host port as a well as a way to access this port number in host.list.
This ticket may be substantially constrained by the Docker API, and there may be some better way to accomplish this. The end result of this ticket might therefore be further tickets if the implementation seems like it will take more work than a single ticket.