Merge branch 'stable-2.14' into stable-2.15

* stable-2.14:
  Update JGit to 4.7.5.201810051826-r
  ElasticContainer: Use Elasticsearch 6.4.2 for V6_4 tests
  Upgrade elasticsearch-rest-client to 6.4.2
  Upgrade jackson-core to 2.9.7

Change-Id: Ia3e641679225e4897825e003e0ddb3ba764c0b50
tree: f66341144a6ea1b660b24517918ee2f2bd52c851
  1. gerrit-acceptance-tests/
  2. gerrit-elasticsearch/
  3. gerrit-pgm/