Bug#46527 COMMIT AND CHAIN RELEASE does not make sense
Bug#53343 completion_type=1, COMMIT/ROLLBACK AND CHAIN don't
preserve the isolation level
Bug#53346 completion_type has strange effect in a stored
procedure/prepared statement
Added test cases to verify the expected behaviour of :
SET SESSION TRANSACTION ISOLATION LEVEL,
SET TRANSACTION ISOLATION LEVEL,
@@completion_type,
COMMIT AND CHAIN,
ROLLBACK AND CHAIN
..and some combinations of the above
