ROLLBACK which may or may not be useful

There were problems with queries that were executed but didn't seem to
be committed. Trying to patch that up by calling a ROLLBACK on transactions
where the loading of the page isn't stopped after the BEGIN statement's
intended function fails (like with the rememberme cookie in this commit).

lib/util.php

@@ -383,6 +383,7 @@ function common_rememberme($user=null)
 
     if (!$result) {
         common_log_db_error($rm, 'INSERT', __FILE__);
+        $rm->query('ROLLBACK');
         return false;
     }