CLC-4057 Perform health check on background job processing

https://jira.ets.berkeley.edu/jira/browse/CLC-4057

If we get LATEs all the time, it's of interest. Another approach would only announcing LATE-ness when we've passed a certain window of time (say 2 minutes after the last "cluster" timestamp) and not mentioning it otherwise. I decided to hold off on that nuance due to the added complexity, but wouldn't mind incorporating it in the PR.