Pull Docker Connection Details from Docker Bay

Docker conductor should use connection details from one of the user's Docker based bays to build it's client instead of getting connection details from magnum's config file.

The current Docker conductor uses the config value 'host_url' as the connection string for it's Docker client. The ultimate goal of this blueprint is to associate each container with a bay, so that the Docker
conductor can instead use the api_address from the container's bay as the connection string. This way, instead of having people manually change config values, they will just spawn containers in bays.