set is_tls at mg_listen and mg_connect level

tutorials/websocket/websocket-client/main.c

@@ -14,7 +14,7 @@ static const char *s_ca_path = "ca.pem";
 static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_OPEN) {
     c->is_hexdumping = 1;
-  } else if (ev == MG_EV_CONNECT && mg_url_is_ssl(s_url)) {
+  } else if (c->is_tls && ev == MG_EV_CONNECT) {
     struct mg_str ca = mg_file_read(&mg_fs_posix, s_ca_path);
     struct mg_tls_opts opts = {.ca = ca, .name = mg_url_host(s_url)};
     mg_tls_init(c, &opts);