bug fix: fix has_instance to return instance_id

Change-Id: Iff6d2d15f4c3cf24dcfac0a1e5e8b51c17152c90
(cherry picked from commit 9e2e5d1a3ff520938d550923a0b21c6005f04edb)
diff --git a/xos/synchronizer/steps/sync_vspgwctenant.py b/xos/synchronizer/steps/sync_vspgwctenant.py
index 3354690..0b2b209 100644
--- a/xos/synchronizer/steps/sync_vspgwctenant.py
+++ b/xos/synchronizer/steps/sync_vspgwctenant.py
@@ -276,4 +276,4 @@
                           serviceinstance=sitype)
             return False
 
-        return i.instance_id
+        return i.leaf_model.instance_id