Query classification data is unintentionally shared between multiple queries

If more than one COM_QUERY packet is read from the client at the same time, they will all share the query classification data of the first type. This happens as the shared buffer that contains the raw data that was read from the socket also contains the query classification data.

For example, both of the following queries are treated as it they were INSERT statements when executed as a pipelined batch.

INSERT INTO t1 VALUES (1);

COMMIT

This is one of the problems that cause MXS-4419.