set is_tls at mg_listen and mg_connect level

tutorials/http/http-client/main.c

@@ -28,7 +28,7 @@ static void fn(struct mg_connection *c, int ev, void *ev_data) {
     // Connected to server. Extract host name from URL
     struct mg_str host = mg_url_host(s_url);
 
-    if (mg_url_is_ssl(s_url)) {
+    if (c->is_tls) {
       struct mg_tls_opts opts = {.ca = mg_unpacked("/certs/ca.pem"),
                                  .name = mg_url_host(s_url)};
       mg_tls_init(c, &opts);