Merge branch 'stable-2.15'

* stable-2.15:
  ElasticContainer: Use Elasticsearch 6.4.2 for V6_4 tests
  Upgrade elasticsearch-rest-client to 6.4.2

Change-Id: Ice17dc2ce03418d75333a489522c53f376d1a657
tree: 1aefd9c97604a21c199d13a1a1a83b741cc10713
  1. java/
  2. javatests/