Use httputil.DumpRequest to pretty-print unhandled requests

[benmoss]

Right now when the test server receives an unhandled HTTP request, it prints out default representation of the request object, which ends up being humongous (see https://gist.github.com/benmoss/86f69211817e33161aa678cb63e0ca57).

The httputil package offers a pretty printer for request objects that gives you the relevant details while sparing you the rest.

      Received Unhandled Request
      Expected
          <string>: POST /oauth/token HTTP/1.1
          Host: 127.0.0.1:51014
          Accept: application/json
          Accept-Encoding: gzip
          Content-Length: 97
          Content-Type: application/x-www-form-urlencoded
          User-Agent: Go-http-client/1.1

          client_id=test_client&client_secret=test_secret&grant_type=client_credentials&response_type=token
      to be nil

I can't see how we would encounter an error while dumping the request, but maybe someone more knowledgable than I might have an idea why this might be problematic.

[benmoss]

Looks like some flaky tests caused the build failure.

[williammartin]

Hey I reran the tests, we're working on fixing flakiness atm. Thanks for the PR, seems to make sense, will have a closer look later.

[williammartin]

LGTM thanks! Hopefully no one is relying on anything in that stdout though, but I think this is a good change.