Revert "Drop the host flag"

This reverts commit 8bdfe16249.

Going to need that to open up the network space outside of the
container. See https://github.com/moby/moby/issues/28121.

ansible/pre-deploy.yml

@@ -48,4 +48,5 @@
         restart: false
         config:
           DOKKU_LETSENCRYPT_EMAIL: "{{ autonomic_admin_mail }}"
+          JEKYLL_HOST: "{{ domain }}"
           JEKYLL_PORT: "{{ http_port }}"