Upgrade elasticsearch-rest-client to 6.5.1

According to the release notes [1], there are no REST client related
bug fixes in this release. This is just to keep up to date with the
latest version.

Also update ElasticContainer to use version 6.5.1.

[1] https://www.elastic.co/guide/en/elasticsearch/reference/current/release-notes-6.5.1.html

Change-Id: I04a6c545b8d2e3394e1d02431394d4861244ed30
diff --git a/gerrit-elasticsearch/src/test/java/com/google/gerrit/elasticsearch/ElasticContainer.java b/gerrit-elasticsearch/src/test/java/com/google/gerrit/elasticsearch/ElasticContainer.java
index 55ebd5d..7f50bbd 100644
--- a/gerrit-elasticsearch/src/test/java/com/google/gerrit/elasticsearch/ElasticContainer.java
+++ b/gerrit-elasticsearch/src/test/java/com/google/gerrit/elasticsearch/ElasticContainer.java
@@ -53,7 +53,7 @@
       case V6_4:
         return "docker.elastic.co/elasticsearch/elasticsearch-oss:6.4.3";
       case V6_5:
-        return "docker.elastic.co/elasticsearch/elasticsearch-oss:6.5.0";
+        return "docker.elastic.co/elasticsearch/elasticsearch-oss:6.5.1";
     }
     throw new IllegalStateException("No tests for version: " + version.name());
   }