CI flaky with Elasticsearch docker image 6.8.6

Some example failures:

I think the problem is visible in the logs as:

2021-02-09T04:54:14.390308551Z [1]: max virtual memory areas vm.max_map_count [65530] is too low, increase to at least [262144]

I think this is a problem only with our docker 6.8.6 startup command. We may wish to look for a different version or provide different startup commands so that it isn't running in production mode per some discussion at https://github.com/elastic/elasticsearch-docker/issues/92#issuecomment-323133779 .