ostree-fetcher-curl: retry requests that fail except NOT_FOUND

This will return G_IO_ERROR_TIMED_OUT with any call
that fails except on cases were the call returns a
NOT_FOUND error. This will trigger a retry.

src/libostree/ostree-fetcher-curl.c

@@ -329,7 +329,11 @@ check_multi_info (OstreeFetcher *fetcher)
             }
           else
             {
-              g_task_return_new_error (task, G_IO_ERROR, G_IO_ERROR_FAILED,
+              /* When it is not a file, we want to retry the request.
+               * We accomplish that by using G_IO_ERROR_TIMED_OUT.
+               */
+              int g_io_error_code = is_file ? G_IO_ERROR_FAILED : G_IO_ERROR_TIMED_OUT;
+              g_task_return_new_error (task, G_IO_ERROR, g_io_error_code,
                                        "While fetching %s: [%u] %s", eff_url, curlres,
                                        curl_easy_strerror (curlres));
               _ostree_fetcher_journal_failure (req->fetcher->remote_name,