Add support for Elasticsearch version 7.4.*

Upgrade elasticsearch-rest-client to 7.4.0.

Add V7_4 to the version manager, and use this in all the V7 tests.

Use the 7.4.0 image from blacktop in the test container.

Change-Id: Ib993f078c142afe34d6f6be83f745464c16b0d2e
8 files changed
tree: fa3c935b6e64ce0dd27de2723d035920a9294199
  1. gerrit-acceptance-tests/
  2. gerrit-elasticsearch/
  3. gerrit-pgm/