This is a partial cherry-pick of 9f11fdd2c122c9b30548c7ab55df8dda643ec659.
Use larger BLOB type for mxs812_1, the inserted value exceeds the normal
BLOB size.
Add a baseline check into bulk_insert to verify that direct connections
work (at the moment they don't, needs an investigation).
Modified avro_alter to prevent data type conversion errors.
The avrorouter failed to detect ALTER TABLE statements which caused a
regression. Extended the alter table tests to parse the JSON for more
strict validation of test results.
