MDEV-15373 engine gtid_slave_pos table name disobeys lower-case-table-names

Replicated transaction extra gtid statement on slave failed to specify
an engine gtid_slave_pos name correctly. In case  lower-case-table-names > 0
the InnoDB table name was generated to reproduce the lower-case-table-names=0 version
which is of mixed cases.
In rpl.rpl_mdev12179 test run this triggered a failure to DROP table which
was due to the innodb table handle was not closed:
 InnoDB: Waited XYZ seconds for ref-count on table: `mysql`.`gtid_slave_pos_innodb`
on windows.
The closing issue was caused by having the table registered twice in the table cache,
for its lower- and mixed- case name versions. The DROP-table handler closed only
only one of the cache item to leave the 2nd one active.
(On Linux a failure occurs earlier at attempt to open an expected lower-cased table:

  Last_Error: Error during XID COMMIT: failed to update GTID state in mysql.gtid_slave_pos: 1146: Table 'mysql.gtid_slave_pos_InnoDB' doesn't exist

but the table's name as the message shows is not in the right case).

Fixed with consulting lower-case-table-names when the engine gtid-slave-pos table
is created.
Note the lower-case-table-names=a-value created table will not recognized when next
the lower case option changes to a different value.
In 10.4 a follow-up patch is going to lowercase gtid-slave-pos autocreated table
at once at their origination, and a warning is issued in the 10.3 current patch.

1 files changed, 1 insertions, 0 deletions

diff --git a/sql/rpl_rli.cc b/sql/rpl_rli.cc
index 70b5832b274..05dffe2c462 100644
--- a/sql/rpl_rli.cc
+++ b/sql/rpl_rli.cc
@@ -1780,6 +1780,7 @@ gtid_pos_auto_create_tables(rpl_slave_state::gtid_pos_table **list_ptr)
     p= strmake(p, plugin_name(*auto_engines)->str, FN_REFLEN - (p - buf));
     table_name.str= buf;
     table_name.length= p - buf;
+    table_case_convert(const_cast<char*>(table_name.str), table_name.length);
     entry= rpl_global_gtid_slave_state->alloc_gtid_pos_table
       (&table_name, hton, rpl_slave_state::GTID_POS_AUTO_CREATE);
     if (!entry)