Follow up to previous commit for codership/mysql-wsrep#332

Fix misplaced `DBUG_RETURN` in `Alter_table_statement::execute`.

sql/sql_alter.cc

@@ -123,6 +123,7 @@ bool Alter_table_statement::execute(THD *thd)
                             select_lex->order_list.first,
                             lex->ignore, lex->online);
 
+  DBUG_RETURN(result);
 #ifdef WITH_WSREP
 error:
   {
@@ -130,5 +131,4 @@ bool Alter_table_statement::execute(THD *thd)
     DBUG_RETURN(TRUE);
   }
 #endif /* WITH_WSREP */
-  DBUG_RETURN(result);
 }