Remove ListImagesTest from test_images

ListImagesTest is now only inherited by ListUserImagesTest,
so it can be removed to reduce the depth of the class inheritance.

Change-Id: I4f1478283f7e66fa3bd5cb4d8692edf299ea2a85
diff --git a/tempest/api/image/v2/test_images.py b/tempest/api/image/v2/test_images.py
index cdf0b23..36dc6c3 100644
--- a/tempest/api/image/v2/test_images.py
+++ b/tempest/api/image/v2/test_images.py
@@ -126,11 +126,12 @@
         self.assertEqual(new_image_name, body['name'])
 
 
-class ListImagesTest(base.BaseV2ImageTest):
+class ListUserImagesTest(base.BaseV2ImageTest):
+    """Here we test the listing of image information"""
 
     @classmethod
     def resource_setup(cls):
-        super(ListImagesTest, cls).resource_setup()
+        super(ListUserImagesTest, cls).resource_setup()
         # We add a few images here to test the listing functionality of
         # the images API
         container_fmts = CONF.image.container_formats
@@ -166,10 +167,6 @@
 
         return image['id']
 
-
-class ListUserImagesTest(ListImagesTest):
-    """Here we test the listing of image information"""
-
     def _list_by_param_value_and_assert(self, params):
         """Perform list action with given params and validates result."""
         # Retrieve the list of images that meet the filter
@@ -323,7 +320,7 @@
         self.assertEqual("images", body['name'])
 
 
-class ListSharedImagesTest(ListImagesTest):
+class ListSharedImagesTest(base.BaseV2ImageTest):
     """Here we test the listing of a shared image information"""
 
     credentials = ['primary', 'alt']