Add test list namespace function

Both test_images.py and test_images_member.py have test list funtion,
we can also add a function in test_images_metadefs_namespaces.py for
testing namespaces list.

Another reason is we have done create, get detail, update and delete
namespace test. But did not test the list.

Related link:
http://developer.openstack.org/api-ref/image/v2/metadefs-index.html

Change-Id: I4caaccec9dea29f6a368f013a3edaad893fafada

tempest/api/image/v2/test_images_metadefs_namespaces.py

@@ -40,6 +40,10 @@ class MetadataNamespacesTest(base.BaseV2ImageTest):
             protected=True)
         self.addCleanup(test_utils.call_and_ignore_notfound_exc,
                         self._cleanup_namespace, namespace_name)
+        # list namespaces
+        bodys = self.namespaces_client.list_namespaces()['namespaces']
+        body = [namespace['namespace'] for namespace in bodys]
+        self.assertIn(namespace_name, body)
         # get namespace details
         body = self.namespaces_client.show_namespace(namespace_name)
         self.assertEqual(namespace_name, body['namespace'])

tempest/lib/services/image/v2/namespaces_client.py

@@ -34,6 +34,18 @@ class NamespacesClient(rest_client.RestClient):
         body = json.loads(body)
         return rest_client.ResponseBody(resp, body)
 
+    def list_namespaces(self):
+        """List namespaces
+
+        Available params: see http://developer.openstack.org/
+                              api-ref/image/v2/metadefs-index.html#list-namespaces
+        """
+        url = 'metadefs/namespaces'
+        resp, body = self.get(url)
+        self.expected_success(200, resp.status)
+        body = json.loads(body)
+        return rest_client.ResponseBody(resp, body)
+
     def show_namespace(self, namespace):
         """Show namespace details.