Add support for Elasticsearch 7.1.0

Update the REST client to 7.1.0. Introduce a new V7_1 version, and
use that in all V7 tests.

Change-Id: I313a802dda0e2c2a0905de1f6a186cf084848938
7 files changed
tree: f5d3263b93d1d7fc95eb3f79d64afbfb66b35285
  1. gerrit-acceptance-tests/
  2. gerrit-elasticsearch/
  3. gerrit-pgm/