rabbitmq://localhost/vhost_name/queue_name
is all you need. We use vhosts for most things, and just try to keep it simple :)
You can see the code pulling it out here: https://github.com/MassTransit/MassTransit/blob/v2.7.2/src/Transports/MassTransit.Transports.RabbitMq/RabbitMqEndpointAddress.cs#L167