CORD-2273: Use defer_sync to delay synchronization

Change-Id: I84b368e63d70b82f353795879479d3d2fd5e3006
diff --git a/xos/synchronizer/steps/sync_venbserviceinstance.py b/xos/synchronizer/steps/sync_venbserviceinstance.py
index 3f48e05..eb1e0dd 100644
--- a/xos/synchronizer/steps/sync_venbserviceinstance.py
+++ b/xos/synchronizer/steps/sync_venbserviceinstance.py
@@ -67,6 +67,7 @@
         except Exception:
             ip_address = "error"
             self.log.error("Could not fetch parameter", parameter = parameter, network_name = network_name)
+            self.defer_sync("Waiting for parmaters to become available")
 
         return ip_address