ElasticReindexIT: Add tests against Elasticsearch version 6

Bug: Issue 9112
Change-Id: I04f275dd930308d610320dcd072522d018535157
diff --git a/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/pgm/ElasticReindexIT.java b/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/pgm/ElasticReindexIT.java
index d7fcd38..071600e 100644
--- a/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/pgm/ElasticReindexIT.java
+++ b/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/pgm/ElasticReindexIT.java
@@ -51,6 +51,11 @@
     return getConfig(ElasticVersion.V5_6);
   }
 
+  @ConfigSuite.Config
+  public static Config elasticsearchV6() {
+    return getConfig(ElasticVersion.V6_2);
+  }
+
   @Override
   public void configureIndex(Injector injector) throws Exception {
     ElasticTestUtils.createAllIndexes(injector);