Cut over to batched DNS refreshing on host renames

TESTED=I deployed it on alpha, renamed some hosts, and verified that
the [] ran as expected.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=134991941

java/google/registry/config/TestRegistryConfig.java

@@ -166,9 +166,4 @@ public class TestRegistryConfig implements RegistryConfig {
   public String getCheckApiServletRegistrarClientId() {
     return "TheRegistrar";
   }
-
-  @Override
-  public Duration getAsyncFlowFailureBackoff() {
-    return Duration.standardMinutes(10);
-  }
 }