Make all but one field on RegistryConfig static

The next step will be to get rid of RegistryConfig descendants and RegistryConfigLoader entirely.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=143812815

java/google/registry/model/registrar/Registrar.java

@@ -24,6 +24,7 @@ import static com.google.common.base.Strings.emptyToNull;
 import static com.google.common.base.Strings.nullToEmpty;
 import static com.google.common.collect.Sets.immutableEnumSet;
 import static com.google.common.io.BaseEncoding.base64;
+import static google.registry.config.RegistryConfig.getRegistrarDefaultWhoisServer;
 import static google.registry.model.common.EntityGroupRoot.getCrossTldKey;
 import static google.registry.model.ofy.ObjectifyService.ofy;
 import static google.registry.model.ofy.Ofy.RECOMMENDED_MEMCACHE_EXPIRATION;
@@ -446,10 +447,7 @@ public class Registrar extends ImmutableObject implements Buildable, Jsonifiable
   }
 
   public String getWhoisServer() {
-    if (whoisServer == null) {
-      return ENVIRONMENT.config().getRegistrarDefaultWhoisServer();
-    }
-    return whoisServer;
+    return firstNonNull(whoisServer, getRegistrarDefaultWhoisServer());
   }
 
   public boolean getBlockPremiumNames() {