Confusing error message when trying to start transaction in OLAP workload mode

[aquarapid]

In Vitess 9.0: If you switch to workload=OLAP and start a transaction (either via, start transaction or begin) you get a strange error message, e.g.:

mysql> set workload=olap;
Query OK, 0 rows affected (0.00 sec)

mysql> start transaction;
ERROR 1105 (HY000): vtgate: http://localhost:15001/: unrecognized VSTREAM statement: start transaction

Yes, transactions are not supported in OLAP mode; but what does that have to do with VSTREAM?

[deepthi]

For future reference, the error message we produce after the fix is "unsupported statement type for OLAP".