Restricts retrying for 400 error codes to just 429

Author: LiuJoyceC

lib/util.js

@@ -841,7 +841,7 @@ var util = {
           } else {
             var retryAfter = parseInt(httpResponse.headers['retry-after']) * 1000 || 0;
             var err = util.error(new Error(),
-              { retryable: !!(statusCode >= 500 || (statusCode >= 400 && retryAfter)) }
+              { retryable: statusCode >= 500 || statusCode === 429 }
             );
             if (retryAfter && err.retryable) err.retryAfter = retryAfter;
             errCallback(err);