bug fix: get_ mac_address function

Change-Id: Icb7e17915b8a5a264b2e439ecb751410e2a5e4fa
diff --git a/xos/synchronizer/steps/sync_vspgwutenant.py b/xos/synchronizer/steps/sync_vspgwutenant.py
index 1a5cca0..58fe97f 100644
--- a/xos/synchronizer/steps/sync_vspgwutenant.py
+++ b/xos/synchronizer/steps/sync_vspgwutenant.py
@@ -273,10 +273,10 @@
 
         return ip_address
 
-    def get_mac_address_from_peer_service_instance_instance(self, network_name, service_instance, o, parameter):
+    def get_mac_address_from_peer_service_instance_instance(self, network_name, peer_si, o, parameter):
         try:
             net_id = self.get_network_id(network_name)
-            ins_id = self.get_instance_id(service_instance)
+            ins_id = peer_si.leaf_model.instance_id
             mac_address = Port.objects.get(network_id=net_id, instance_id=ins_id).mac
 
         except Exception: