Delete the image diff feature

Fixes #1077

initdb.py

@@ -118,13 +118,6 @@ def __create_subtree(repo, structure, creator_username, parent, tag_map):
     model.image.set_image_size(docker_image_id, repo.namespace_user.username, repo.name,
                                compressed_size, int(compressed_size * 1.4))
 
-    # Populate the diff file
-    diff_path = store.image_file_diffs_path(new_image.storage.uuid)
-    source_diff = SAMPLE_DIFFS[image_num % len(SAMPLE_DIFFS)]
-
-    with open(source_diff, 'r') as source_file:
-      store.stream_write(new_image_locations, diff_path, source_file)
-
     parent = new_image
 
   if last_node_tags: