auth tests should not require admin token

Currently all the v3 auth tests are calling self.post(), which
eventually going through keystone.tests.test_v3.v3_request().
The v3_request method always requires an auth token by default.
But since V3 auth token API is an unprotected API, there's no need
for an auth token in order to make the request.

Change-Id: If65305346c0e5e114fd03e4ba089aa2e3694a8b2
Closes-bug: #1317261

keystone/tests/test_v3.py

@@ -423,21 +423,21 @@ def get_scoped_token(self):
     def get_requested_token(self, auth):
         """Request the specific token we want."""
 
-        r = self.admin_request(
-            method='POST',
-            path='/v3/auth/tokens',
-            body=auth)
+        r = self.v3_authenticate_token(auth)
         return r.headers.get('X-Subject-Token')
 
+    def v3_authenticate_token(self, auth, expected_status=201):
+        return self.admin_request(method='POST',
+                                  path='/v3/auth/tokens',
+                                  body=auth,
+                                  expected_status=expected_status)
+
     def v3_noauth_request(self, path, **kwargs):
         # request does not require auth token header
         path = '/v3' + path
         return self.admin_request(path=path, **kwargs)
 
     def v3_request(self, path, **kwargs):
-        # TODO(gyee): need to fix all the v3 auth tests. They should not
-        # require the token header.
-
         # check to see if caller requires token for the API call.
         if kwargs.pop('noauth', None):
             return self.v3_noauth_request(path, **kwargs)