Fix assertion `thd->in_active_multi_stmt_transaction() ||
thd->m_transaction_psi == __null' failed on MTR test
galera_sr.GCF-1051.
Add a new MTR test MDEV-23623 that reproduces the issue
deterministically and update wsrep-lib submodule, containing
the actual fix.
Reviewed-by: Jan Lindström <jan.lindstrom@mariadb.com>
