Fix Elasticsearch index create race in tests

[kitcommerce]

Extracted from stacked PRs #630/#631 (commit 7e64d18).

Makes Elasticsearch index creation in tests resilient to a race.

Target: next.

[kitcommerce]

Build Gate Failed

rubocop

Rakefile:80:11 Layout/SpaceAroundOperators Operator `<<` should be surrounded by a single space.
core/lib/workarea/configuration.rb:955:7 Layout/CommentIndentation Incorrect indentation detected (column 6 instead of 0).
core/lib/workarea/ext/freedom_patches/bson_document.rb:10:1 Layout/TrailingWhitespace Trailing whitespace detected.
core/test/lib/workarea/elasticsearch/document_test.rb:114:1 Layout/TrailingWhitespace Trailing whitespace detected.

Branch: test-es-index-create-race
PR: #651

These appear to be existing style issues in this branch; once fixed + pushed, re-apply status:ready-for-review and the dispatcher will re-run build gate + review waves.