Change data_processing client to return one value and update tests

Two methods returned string data and so were left as returning resp,data

Partially implements: blueprint clients-return-one-value

Change-Id: I08c8e8b3dd61e85afca174a8e4b3148e7ac6452a
diff --git a/tempest/api/data_processing/test_cluster_templates.py b/tempest/api/data_processing/test_cluster_templates.py
index 537f90c..422ea5b 100644
--- a/tempest/api/data_processing/test_cluster_templates.py
+++ b/tempest/api/data_processing/test_cluster_templates.py
@@ -120,7 +120,7 @@
         template_info = self._create_cluster_template()
 
         # check for cluster template in list
-        _, templates = self.client.list_cluster_templates()
+        templates = self.client.list_cluster_templates()
         templates_info = [(template['id'], template['name'])
                           for template in templates]
         self.assertIn(template_info, templates_info)
@@ -130,7 +130,7 @@
         template_id, template_name = self._create_cluster_template()
 
         # check cluster template fetch by id
-        _, template = self.client.get_cluster_template(template_id)
+        template = self.client.get_cluster_template(template_id)
         self.assertEqual(template_name, template['name'])
         self.assertDictContainsSubset(self.cluster_template, template)