Pruning boundary for history partitions is wrong by 1 second

-- source include/have_partition.inc

set timestamp= unix_timestamp('2000-01-01 00:00:00');

create or replace table t1 (x int) with system versioning

partition by system_time interval 1 hour

(partition p0 history, partition pn current);

insert into t1 values (330);

set timestamp= unix_timestamp('2000-01-01 00:10:00');

update t1 set x= x + 1;

--echo # Check how pruning boundaries work

explain partitions select * from t1 for system_time as of '2000-01-01 00:59:58';

explain partitions select * from t1 for system_time as of '2000-01-01 00:59:59';

drop tables t1;

explain partitions select * from t1 for system_time as of '2000-01-01 00:59:59';

id      select_type     table   partitions      type    possible_keys   key     key_len ref     rows    Extra

1       SIMPLE  t1      pn      system  NULL    NULL    NULL    NULL    1

explain partitions select * from t1 for system_time as of '2000-01-01 00:59:59';

id      select_type     table   partitions      type    possible_keys   key     key_len ref     rows    Extra

1       SIMPLE  t1      p0, pn      system  NULL    NULL    NULL    NULL    1