Allow none override + cleanup

Related-Bug: PROD-21498 (PROD:21498)

Change-Id: If14e1e335818b802d163c4178b46ab8e226dc892
diff --git a/reclass/storage/salt.yml b/reclass/storage/salt.yml
index 0a21cdb..b2025c4 100644
--- a/reclass/storage/salt.yml
+++ b/reclass/storage/salt.yml
@@ -8,6 +8,8 @@
         engine: git
         address: '${_param:reclass_data_repository}'
         branch: ${_param:reclass_data_revision}
+
+  # TODO, remove this once not required for backward compatibility
   salt:
     master:
       pillar: