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/Irc/lib/ircmanager.php

@@ -245,7 +245,6 @@ class IrcManager extends ImManager {
                         common_log_db_error($confirm, 'DELETE', __FILE__);
                         // TRANS: Server error thrown on database error when deleting IRC nickname confirmation.
                         $this->serverError(_m('Could not delete confirmation.'));
-                        return;
                     }
                 }
             }