Fixed #15362: Added explicit deletion of file to test, needed now since files...

Fixed #15362: Added explicit deletion of file to test, needed now since files are no longer auto-deleted when a referencing object is deleted. Thanks mila.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@15602 bcc190cf-cafb-0310-a4f2-bffc1f526a37