A role used to register hosts to Rancher's server, by running rancher_agent Docker container and providing the agent with the name and the registration script.
rancher_server: The IP of Rancher platform.
rancher_port: The port of Rancher platform.
rancher_agent_name: The name of the agent container.
rancher_agent_version: The version of the agent.
This role requires Docker to be installed on the server.