10.4-MDEV-29684 Fixes for cluster wide write conflict resolving

The rather recent thd_need_ordering_with() function does not take
high priority transactions' order in consideration. Chaged this
funtion to compare also transaction seqnos and favor earlier transaction.

Reviewed-by: Jan Lindström <jan.lindstrom@mariadb.com>

sql/sql_class.cc

@@ -5230,8 +5230,9 @@ thd_need_ordering_with(const MYSQL_THD thd, const MYSQL_THD other_thd)
      (e.g. InnoDB does it by keeping lock_sys.mutex locked)
   */
   if (WSREP_ON &&
-      wsrep_thd_is_BF(const_cast<THD *>(thd), false) &&
-      wsrep_thd_is_BF(const_cast<THD *>(other_thd), false))
+      wsrep_thd_is_BF(thd, false) &&
+      wsrep_thd_is_BF(other_thd, false) &&
+      wsrep_thd_order_before(thd, other_thd))
     return 0;
 #endif /* WITH_WSREP */
   rgi= thd->rgi_slave;