Fix #948: ensure the admin panel is disabled

tests/compose/webmail/01_ensure_admin_unreachable.sh

@@ -0,0 +1,4 @@
+#!/bin/sh
+
+[[ `curl -I -so /dev/null -w "%{http_code}" http://localhost/` -ne 200 ]] && echo "The default page of rainloop hasn't returned 200!" >>/dev/stderr && exit 1
+[[ `curl -I -so /dev/null -w "%{http_code}" http://localhost/?admin` -ne 403 ]] && echo "The admin of rainloop is not disabled!" >>/dev/stderr && exit 1