add tearDown to a case test

fixes couchforms test:

======================================================================
FAIL: test_basic_edit (couchforms.tests.test_edits.EditFormTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "./corehq/ex-submodules/couchforms/tests/test_edits.py", line 49, in test_basic_edit
    self.assertEqual(self.ID, doc.orig_id)
AssertionError: '7H46J37FGH3' != u'6RGAZTETE3Z2QC0PE2DKM88MO'

----------------------------------------------------------------------