Missing image-del func in test_create_delete_image

* Test Case test_create_delete_image is missing image-delete
  functionality and the image is left undeleted after running this
  test. So adding image-delete functionality to test the delete
  function.

* This is a smoke test that tests create & delete image functionality.

Change-Id: I14fa4e65b83791f3effc2ca5694d363e2b7f09bd
diff --git a/tempest/tests/compute/images/test_images_oneserver.py b/tempest/tests/compute/images/test_images_oneserver.py
index ca3dbb5..bcd09f6 100644
--- a/tempest/tests/compute/images/test_images_oneserver.py
+++ b/tempest/tests/compute/images/test_images_oneserver.py
@@ -130,6 +130,11 @@
         self.assertEqual(original_image['minRam'], image['minRam'])
         self.assertEqual(original_image['minDisk'], image['minDisk'])
 
+        # Verify the image was deleted correctly
+        resp, body = self.client.delete_image(image_id)
+        self.assertEqual('204', resp['status'])
+        self.assertRaises(exceptions.NotFound, self.client.get_image, image_id)
+
     @attr(type='negative')
     @testtools.skipUnless(compute.MULTI_USER,
                           'Need multiple users for this test.')