Revert "remove refresh-token check that is no longer needed"

This reverts commit bd6e408.

Author: ylebre

solid/lib/Controller/ServerController.php

@@ -109,7 +109,9 @@ private function createAuthServerConfig() {
 		if (isset($_GET['client_id'])) {
 			$clientId = $_GET['client_id'];
 		} else if (isset($_POST['client_id'])) {
-			$clientId = $_POST['client_id'];
+			if (isset($_POST['refresh_token'])) { // FIXME: Why does the test suite break without this?
+				$clientId = $_POST['client_id'];
+			}
 		}
 		$client = $this->getClient($clientId);
 		$keys = $this->getKeys();