stop masking low-level request/response errors

Our algorithm function `log_result_of_request` (`lror`) was too brittle. It didn't know what to do if it was called without both a request and a response object. If we don't have a request or response object it basically means we're handling an error. It's usually the case that errors are still logged: the stock algorithm has `log_traceback_for_5xx`; Gittip adds `tell_sentry`. But cases can be imagined where `lror` would in fact swallow an exception, and in the best scenario it simply results in lots of log spam.