Inspired by https://bugs.chromium.org/p/chromium/issues/detail?id=698773 (however, not sure this will actually address that problem, because the error wasn't on the create job page, but on a javascript action from a button on that page?)

Add a basic test in the push to prod that runs curl against a few URLs of the autotest web UI, and ensures that they return http-200.

This protects us against pushes that catastrophically break the autotest UI.

As I said though, I'm not sure this would actually have protected us in 698773