The special TRUNCATE TABLE (DDL) transaction wasn't being properly
rolled back if a error occurred during row by row deletion. The
error can be caused by a foreign key restriction imposed by InnoDB
SE and would cause the server to erroneously issue a implicit
commit.

The solution is to rollback the transaction if a truncation via row
by row deletion fails, otherwise commit. All effects of a TRUNCATE 
ABLE operation are rolled back if a row by row deletion fails.