Undefined array key warning in WP CLI

**Steps to reproduce**

1. Go to the Altis Dashboard.
2. Open a CLI session
3. See this warning at the top of the console:
```
Warning: Undefined array key "HTTP_HOST" in phar:///usr/local/bin/wp/vendor/wp-cli/wp-cli/php/WP_CLI/Runner.php(1309) : eval()'d code on line 45
Warning: Undefined array key "HTTP_HOST" in /usr/src/app/wordpress/wp-includes/ms-settings.php on line 57
```

**Describe what you expected to see**

Silence this warning.

I assume we need to set the `HTTP_HOST` key when in a CLI context. I remember we maybe did this on various HM platform sites, but not sure.

Either way having this warning repeatedly during CLI operations looks poor and it's annoying.