Check the status of the notebook itself

Turns out the port is up (nearly) instantaneously, but we still have to wait for the Notebook server to boot up. This rolls through until an HTTP Error isn't seen anymore.

Side questions: Are there ways to optimize starting a notebook server? This one does launch straight from `master`.
I tossed back and forth on whether I should even include the connection test. In my repeated tests, I only ever got the HTTP errors. I'd like to log it to see if we ever hit the issue.