Wait for server to be ready when starting container

Some models take some time to start up, especially in Julia when many packages need to be loaded in. If you try to connect immediately, you will get an error. However, if you wait a few seconds things go fine.

It would be more user-friendly if there was a timeout and a check to see if the server is alive and reachable. This way we can make the python process wait (and thus communicate to users that the server isn't ready yet).