fix a test by making CommCareUserResource disallow stale couch results

Failure looked like:

```
FAIL: test_get_list (corehq.apps.api.tests.TestCommCareUserResource)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/droberts/dimagi/commcare-hq/corehq/apps/api/tests.py", line 209, in test_get_list
    self.assertEqual(len(api_users), 1)
AssertionError: 0 != 1
```