The sensitive information should be dumped to `app/etc/env.php` instead of `app/etc/config.php` on `bin/magento app:config:dump` to better support the Magento 2.2 «Pipeline Deployment»

[dmitrii-fediuk]

devdocs.magento.com/guides/v2.2/config-guide/cli/config-cli-subcommands-config-mgmt-export.html