Merge branch 'stable-2.15' into stable-2.16

* stable-2.15:
  Elasticsearch: Add support and tests for version 7.2
  js.bzl: Stop using invalid join call

Also adjust ElasticV7QueryProjectsTest to use V7_2.

Change-Id: Ieba5f019a4f7ebe08ea42f8a29840aa496a4abf0

javatests/com/google/gerrit/elasticsearch/ElasticContainer.java

@@ -54,6 +54,8 @@ public class ElasticContainer extends ElasticsearchContainer {
         return "blacktop/elasticsearch:7.0.1";
       case V7_1:
         return "blacktop/elasticsearch:7.1.1";
+      case V7_2:
+        return "blacktop/elasticsearch:7.2.0";
     }
     throw new IllegalStateException("No tests for version: " + version.name());
   }