Add test namespace object functions in images

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

Co-Authored-By: guo yunxian <yunxian.guo@easystack.cn>
Change-Id: Ic60e3c78ade0eefe21f79c6bfb716beb13b08483
diff --git a/releasenotes/notes/add-image-clients-tests-49dbc0a0a4281a77.yaml b/releasenotes/notes/add-image-clients-tests-49dbc0a0a4281a77.yaml
new file mode 100644
index 0000000..9d1a003
--- /dev/null
+++ b/releasenotes/notes/add-image-clients-tests-49dbc0a0a4281a77.yaml
@@ -0,0 +1,9 @@
+---
+features:
+  - |
+    As in the [doc]:
+    http://developer.openstack.org/api-ref/image/v2/metadefs-index.html,
+    there are some apis are not included, add them.
+
+      * namespace_objects_client(v2)
+