Move shared V1/V2 code into common methods and fix verbs

data/model/storage.py

@@ -216,3 +216,14 @@ def get_repo_storage_by_checksum(namespace, repository_name, checksum):
     return _get_storage(filter_to_repo_and_checksum)
   except InvalidImageException:
     raise InvalidImageException('No storage found with checksum {0}'.format(checksum))
+
+
+def get_layer_path(storage_record, store):
+  """ Returns the path in the storage engine to the layer data referenced by the storage row. """
+  if not storage_record.cas_path:
+    return store.v1_image_layer_path(storage_record.uuid)
+
+  return store.blob_path(storage_record.checksum)
+
+
+