BINLOG_FORMAT_MIXED is not supported

[Seppo Jaakola]

Using binlog format "mixed", will cause an (debug) assert inside log.cc
(log.cc:: MYSQL_BIN_LOG::write(), line: 4409)

Assert is like:
DBUG_ASSERT((int) thd->variables.binlog_format == BINLOG_FORMAT_ROW ||
                 mysql_bin_log.is_open());

To reproduce, just set binlog_format=MIXED

This issue prevents mysql tetst suite test 'innodb' to complete

[Seppo Jaakola (seppo-jaakola)]

MIXED format is actually STATEMENT format, with fall back to ROW format under certain conditions. This causes issue for "binlog emulation", in wsrep code.

My first take on this is just to disable MIXED format as wsrep works best in ROW format.