Remove non_transactional flag from UsageEvent repo specs

* We stubbed truncate with dataset.destroy for test only. It should have the
  same behavior, but will not autocommit the transaction in mysql.
* Removing the non_transactional flag will greatly increase the speed of each
  spec affected

[#71446796]

Signed-off-by: James Myers <jmyers@pivotallabs.com>
Reseed stacks when resetting the database in test

[#71446796]

Signed-off-by: James Myers <jmyers@pivotallabs.com>
Remove non_transactional flag from service broker specs

* It appears as if only one spec, "does not delete the broker", depended on
  the non_transactional behavior.

[#71446796]

Signed-off-by: Michael Fraenkel <fraenkel@us.ibm.com>