fix `Elasticsearch::Transport::Transport::Errors::ServiceUnavailable: [503]`

elasticsearch_cleaner.rb

# fixed: Elasticsearch::Transport::Transport::Errors::ServiceUnavailable: [503]
# https://hugotunius.se/2015/06/22/elasticsearch-falkiness-in-tests.html
# https://medium.com/@thetron/dealing-with-503-errors-when-testing-elasticsearch-integration-in-rails-ec7a5f828274#.ex6quza03
# https://github.com/elastic/elasticsearch-ruby/issues/181#issuecomment-112781924

# spec/support/elasticsearch_cleaner.rb
RSpec.configure do |config|
  config.before(:each, :es => true) do
    ElasticsearchModel.create_index!(:force => true)
    ElasticsearchModel.client.cluster.health(wait_for_status: 'yellow')
  end
end