Investigate MDL BF-BF cases

Following existing test cases are affected:

• galera.galera_create_table_as_select

  w7 [ fail ] Found warnings/errors in server log file!

  Test ended at 2025-12-12 10:45:16

  line

  2025-12-12 10:45:06 2 [ERROR] WSREP: MDL conflig-> abort request BF:2:CREATE TABLE `t1` (

• galera.MDEV-22232

  w3 [ fail ] Found warnings/errors in server log file!

  Test ended at 2025-12-12 10:45:59

  line

  2025-12-12 10:45:48 60 [ERROR] WSREP: MDL conflig-> abort request BF:60:TRUNCATE TABLE t1 granted BF:61 query CREATE TABLE t2 SELECT * FROM t1

  2025-12-12 10:45:48 60 [ERROR] WSREP: MDL conflig-> abort request BF:60:TRUNCATE TABLE t1 granted BF:61 query CREATE TABLE t2 SELECT * FROM t1

• galera.MDEV-32938

  w3 [ fail ] Found warnings/errors in server log file!

  Test ended at 2025-12-12 10:47:34

  line

  2025-12-12 10:47:23 94 [ERROR] WSREP: MDL conflig-> abort request BF:94:ALTER TABLE t1 ADD COLUMN c3 INT granted BF:95 query ALTER TABLE t1 DROP COLUMN c2

• galera.MW-286

  w6 [ fail ] Found warnings/errors in server log file!

  Test ended at 2025-12-12 10:48:18

  line

  2025-12-12 10:48:07 1 [ERROR] WSREP: MDL conflig-> abort request BF:1:INSERT INTO t1(f1) VALUES (11)��;i granted BF:129 query ALTER TABLE t1 ADD PRIMARY KEY (f1)