Cosmetic changes to common_redirect, clientError, serverError

Since these functions exit (or throw exception) after running, there
is no need to have a 'return' statement or similar afterwards.

plugins/EmailRegistration/actions/emailregister.php

@@ -191,7 +191,6 @@ class EmailregisterAction extends Action
 
         if (!empty($cur)) {
             common_redirect(common_local_url('all', array('nickname' => $cur->nickname)));
-            return;
         }
 
         switch ($this->state) {