Fixes bug 938953 parsing of image id

Change-Id: I8cac92af3cc40174d4acc390913be90fa5a7552c
diff --git a/tempest/tests/test_images.py b/tempest/tests/test_images.py
index c422708..8217d2a 100644
--- a/tempest/tests/test_images.py
+++ b/tempest/tests/test_images.py
@@ -7,8 +7,8 @@
 
 
 def _parse_image_id(image_ref):
-    temp = image_ref.rsplit('/')
-    return temp[6]
+    temp = image_ref.rsplit('images/')
+    return temp[1]
 
 
 class ImagesTest(unittest.TestCase):