Switch to Java 8 on CI Agents
Switch to Java 8 on CI Agents

It's a bit weird that this is done through Elasticsearch I'll try sort
this in a subsequent commit.

alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet