Adjust attempt and wait durations
Adjust attempt and wait durations

* Sleep for less time, check more often.

* Assume that 'ok on first attempt' means CDN already has origin marked
  as ok.

* Also adjust loop logic so that we aren't checking maxRetries twice.

alphagov/cdn-acceptance-tests,alphagov/cdn-acceptance-tests,mikepea/cdn-acceptance-tests,mikepea/cdn-acceptance-tests,mikepea/cdn-acceptance-tests,mikepea/cdn-acceptance-tests,alphagov/cdn-acceptance-tests,alphagov/cdn-acceptance-tests