Comment 3 for bug 1540394

I have to pause on this for now, so unassigning myself in case someone else wants to pick it up.

I think we want to decorate the autorest.Client's Sender such that it retries (for a specified duration) with backoff when a 429 occurs. We may want or need to update azure-sdk-for-go first, as it appears that the API for autorest has changed a bit.