tests: Add tests for how Let's Encrypt ACME challenge is handled

At the moment no changes to functionality are done, only the current
behavior is captured.

test/test_ssl/wildcard_cert_and_nohttps/docker-compose.yml

@@ -7,6 +7,7 @@ services:
     volumes:
       - /var/run/docker.sock:/tmp/docker.sock:ro
       - ./certs:/etc/nginx/certs:ro
+      - ./acme_root:/usr/share/nginx/html:ro
 
   web1:
     image: web