MDEV-33952: Fix flaky galera_create_table_as_select test with debug sync #3246
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Description
The test that triggers multi-master conflict between two CTAS commands uses LOCK/UNLOCK TABLES to block local CTAS from progress. It could result in a race when UNLOCK TABLES command is issued a bit earlier then needed, causing local CTAS to run further and change wsrep transaction state, so that a different code path is taken later and the original error gets overridden, causing the test to fail. The solution is to replace LOCK/UNLOCK TABLES with debug sync points.
Release Notes
The fix is for 10.5+ versions.
How can this PR be tested?
MTR test is fixed an re-enabled.
Basing the PR against the correct MariaDB version
PR quality check