ElasticSearch doesn't run by default on our docker-compose stack.
This generates a few errors and misconfigurations.

Known issues:

• ElasticPress is still enabled, and generates periodic exceptions (visible with xdebug listening on every exception)
• Disabling ElasticPress triggers a fatal error on search page

Fatal error:  Uncaught Error: Class 'ElasticPress\Features' not 
found in /app/source/public/wp-content/themes/planet4-master-theme/src/Search.php:230

• Links on search page have an empty href attribute

Tasks:

• Fix those issues
• Review Makefile config target to enable/disable plugin according to elastic container status