Corrected code in serializers_regress testcase so that, in the case where an...

Corrected code in serializers_regress testcase so that, in the case where an exception has been raised, rollback is called before attempting to leave transaction management.  With the old code the original exception (IntegrityError on InnoDB) was getting hidden by a transaction management error resulting from attempting to leave transaction management with a pending commit/rollback. 


git-svn-id: http://code.djangoproject.com/svn/django/trunk@9773 bcc190cf-cafb-0310-a4f2-bffc1f526a37