Mark test_non_codegen_tinyint_grouping as execute_serially

The test contains an INSERT and some DDL, which is racy if performed in parallel.

Change-Id: I2b88533f45756fcf6372d6ee4eb7edd474087048
Reviewed-on: http://gerrit.ent.cloudera.com:8080/2167
Reviewed-by: Ishaan Joshi <ishaan@cloudera.com>
Reviewed-by: Alex Behm <alex.behm@cloudera.com>
Reviewed-by: Henry Robinson <henry@cloudera.com>
Tested-by: Henry Robinson <henry@cloudera.com>