We've seen failures in CI where DNS lookups fail which cause our
operations against the service to fail, as well as other sorts of
timeouts.
Add a set of helper methods in a new httputil package that helps us do
retries on these operations, and then update our client library to use
them when we are doing GET requests. We also provide a way for non GET
requests to be retried, and use this when updating a lease (since it
is safe to retry multiple requests in this case).