Merge branch 'stable-2.13'

* stable-2.13:
  Drain executor of index change requests before closing index

Change-Id: I2d676adf60d2eab0f9f7602b124574050af0ee3d

gerrit-lucene/src/main/java/com/google/gerrit/lucene/LuceneAccountIndex.java

@@ -205,4 +205,8 @@ public class LuceneAccountIndex
     // to reindex when those change.
     return accountCache.get(id);
   }
+
+  @Override
+  public void stop() {
+  }
 }