Add the ability to control the certbot HTTP bind port

Fixes #330 (Github Issue).

roles/matrix-nginx-proxy/tasks/ssl/setup_ssl_lets_encrypt_obtain_for_domain.yml

@@ -21,7 +21,7 @@
     --name=matrix-certbot
     --user={{ matrix_user_uid }}:{{ matrix_user_gid }}
     --cap-drop=ALL
-    -p 80:8080
+    -p {{ matrix_ssl_lets_encrypt_container_standalone_http_host_bind_port }}:8080
     -v {{ matrix_ssl_config_dir_path }}:/etc/letsencrypt
     -v {{ matrix_ssl_log_dir_path }}:/var/log/letsencrypt
     {{ matrix_ssl_lets_encrypt_certbot_docker_image }}