fix for the use of a deprecated directive in nginx

install/ubuntu/17.04/templates/web/nginx/caching.stpl

@@ -1,7 +1,6 @@
 server {
-    listen      %ip%:%proxy_ssl_port%;
+    listen      %ip%:%proxy_ssl_port% ssl;
     server_name %domain_idn% %alias_idn%;
-    ssl         on;
     ssl_certificate      %ssl_pem%;
     ssl_certificate_key  %ssl_key%;
     error_log  /var/log/%web_system%/domains/%domain%.error.log error;