The runner controller stops the main control loop when starting model instances

[philwinder]

The issue with this is that in every new UI request there's actually two requests, one for the user and one for the session name.

Because the session name comes in just after the user's, the session name job just sits there, scheduled but waiting, until the initial user job has started. Then the main loop comes back around and pulls the second slot.

Refactor so models start in another goroutine to allow the poll loop to continue.