inconsistent transaction isolation level inside mysql.transaction_registry

--source include/galera_cluster.inc

--connection node_1

create table t1 (

  a int primary key,

  s bigint unsigned as row start,

  e bigint unsigned as row end,

  period for system_time(s,e)

) engine=InnoDB with system versioning;

--connection node_2

insert into t1 (a) values (2);

select * from mysql.transaction_registry;

--connection node_1

select * from mysql.transaction_registry;

drop table t1;

--source include/galera_end.inc

select * from mysql.transaction_registry;

transaction_id	commit_id	begin_timestamp	commit_timestamp	isolation_level

36	37	2018-10-09 11:56:08.254080	2018-10-09 11:56:08.255792	REPEATABLE-READ

connection node_1;

select * from mysql.transaction_registry;

transaction_id	commit_id	begin_timestamp	commit_timestamp	isolation_level

36	37	2018-10-09 11:56:08.256453	2018-10-09 11:56:08.256454	READ-COMMITTED

diff --git a/sql/wsrep_mysqld.h b/sql/wsrep_mysqld.h

index 819a56b9f23..3cd5fe91b13 100644

--- a/sql/wsrep_mysqld.h

+++ b/sql/wsrep_mysqld.h

@@ -47,7 +47,6 @@ struct wsrep_thd_shadow {

   uint                 server_status;

   enum wsrep_exec_mode wsrep_exec_mode;

   Vio                  *vio;

-  ulong                tx_isolation;

   const char           *db;

   size_t               db_length;

   my_hrtime_t          user_time;

diff --git a/sql/wsrep_thd.cc b/sql/wsrep_thd.cc

index ce6d9688cb3..c8e6d5533cc 100644

--- a/sql/wsrep_thd.cc

+++ b/sql/wsrep_thd.cc

@@ -160,10 +160,6 @@ static void wsrep_prepare_bf_thd(THD *thd, struct wsrep_thd_shadow* shadow)

   thd->net.vio= 0;

   thd->clear_error();

-  shadow->tx_isolation        = thd->variables.tx_isolation;

-  thd->variables.tx_isolation = ISO_READ_COMMITTED;

-  thd->tx_isolation           = ISO_READ_COMMITTED;

-

   shadow->db            = thd->db.str;

   shadow->db_length     = thd->db.length;

   shadow->user_time     = thd->user_time;

@@ -178,7 +174,6 @@ static void wsrep_return_from_bf_mode(THD *thd, struct wsrep_thd_shadow* shadow)

   thd->server_status          = shadow->server_status;

   thd->wsrep_exec_mode        = shadow->wsrep_exec_mode;

   thd->net.vio                = shadow->vio;

-  thd->variables.tx_isolation = shadow->tx_isolation;

   thd->user_time              = shadow->user_time;

   thd->reset_db(&db);