MDEV-24916 : Assertion `current_stmt_binlog_format == BINLOG_FORMAT_STMT || current_stmt_binlog_format == BINLOG_FORMAT_ROW' failed in THD::is_current_stmt_binlog_format_row

Store old value of binlog format before wsrep code so that
if we bail out because wsrep is not ready for connections
we can restore binlog format correctly.