Fixed wrong usage of global_query_id. (It's not protected by LOCK_thread_count)

sql/sp_head.cc

@@ -1887,9 +1887,7 @@ sp_head::execute_function(THD *thd, Item **argp, uint argcount,
       as one select and not resetting THD::user_var_events before
       each invocation.
     */
-    mysql_mutex_lock(&LOCK_thread_count);
-    q= global_query_id;
-    mysql_mutex_unlock(&LOCK_thread_count);
+    q= get_query_id();
     mysql_bin_log.start_union_events(thd, q + 1);
     binlog_save_options= thd->variables.option_bits;
     thd->variables.option_bits&= ~OPTION_BIN_LOG;