Reenable consistent notification support

Change-Id: I08b50858344d5ea6dd8e2852d45fb31dcbab4660

@@ -88,7 +88,9 @@ public interface Database extends DatabaseProxy<String, byte[]>, Resource<Databa
    * Tells whether the database supports change notifications.
    * @return true if notifications are supported; false otherwise
    */
-  boolean hasChangeNotificationSupport();
+  default boolean hasChangeNotificationSupport() {
+      return true;
+  }
 
   /**
    * Registers a new consumer of StateMachineUpdates.

@@ -234,11 +234,6 @@ public class DefaultDatabase extends AbstractResource<Database> implements Datab
         consumers.remove(consumer);
     }
 
-    @Override
-    public boolean hasChangeNotificationSupport() {
-        return false;
-    }
-
     private class InternalStateMachineWatcher implements TriConsumer<String, Object, Object> {
         @Override
         public void accept(String name, Object input, Object output) {

@@ -366,11 +366,6 @@ public class PartitionedDatabase implements Database {
     }
 
     @Override
-    public boolean hasChangeNotificationSupport() {
-        return false;
-    }
-
-    @Override
     public void registerConsumer(Consumer<StateMachineUpdate> consumer) {
         partitions.forEach(p -> p.registerConsumer(consumer));
     }