Making model-deps optional for synchronizers

Change-Id: I3cf98e4c9b1e014c005ccebe8fc2ad14e1c86968
diff --git a/lib/xos-config/xosconfig/default.py b/lib/xos-config/xosconfig/default.py
index f6469aa..36767e3 100644
--- a/lib/xos-config/xosconfig/default.py
+++ b/lib/xos-config/xosconfig/default.py
@@ -50,7 +50,7 @@
     },
     'keep_temp_files': False,
     'enable_watchers': False,
-    'dependency_graph': '/opt/xos/model-deps',
+    'dependency_graph': None,
     'error_map_path': '/opt/xos/error_map.txt',
     'feefie': {
         'client_user': 'pl'