Accommodate v2 and v3 auth for integration tests

devstack has moved default Keystone API version to v3[1].

[1] https://github.com/openstack-dev/devstack/commit/f4ce44bf3fbf06e53c2ae3ec6aa4996831cf4605

Though the above patch has been reverted, this would help
if devstack removes v2 support in the future.

Change-Id: I393750d00b3712a015e48a3cf38ab5f95bb61dae
Closes-Bug: #1539692
diff --git a/functional/test_conditional_exposure.py b/functional/test_conditional_exposure.py
index 90f7d7a..c1175f1 100644
--- a/functional/test_conditional_exposure.py
+++ b/functional/test_conditional_exposure.py
@@ -42,13 +42,9 @@
                           "Sahara resources availability.")
 
     def _is_sahara_deployed(self):
-        keystone = self.identity_client
         try:
-            keystone.service_catalog.url_for(
-                attr='region',
-                filter_value=self.conf.region,
-                service_type='data-processing',
-                endpoint_type='publicURL')
+            self.identity_client.get_endpoint_url('data-processing',
+                                                  self.conf.region)
         except keystoneclient.exceptions.EndpointNotFound:
             return False
         return True