Added retries for userRateLimitExceeded and rateLimitExceeded.

Author: mderka

gcloud-java-dns/src/main/java/com/google/gcloud/dns/DnsException.java

@@ -31,9 +31,12 @@ public class DnsException extends BaseServiceException {
 
   // see: https://cloud.google.com/dns/troubleshooting
   private static final Set<Error> RETRYABLE_ERRORS = ImmutableSet.of(
+      new Error(429, null),
       new Error(500, null),
       new Error(502, null),
-      new Error(503, null));
+      new Error(503, null),
+      new Error(null, "userRateLimitExceeded"),
+      new Error(null, "rateLimitExceeded"));
   private static final long serialVersionUID = 490302380416260252L;
 
   public DnsException(IOException exception) {