CORD-1010 Fix sync steps in openstack synchronizer

Change-Id: I372e91b3c9603bb2c993c6a1b570cfc395e61b36
diff --git a/xos/synchronizer/steps/sync_ports.py b/xos/synchronizer/steps/sync_ports.py
index d6f1303..cfd697f 100644
--- a/xos/synchronizer/steps/sync_ports.py
+++ b/xos/synchronizer/steps/sync_ports.py
@@ -216,7 +216,8 @@
 
     def delete_ports(self):
         logger.info("sync'ing Ports [delete=True]")
-        for port in Port.deleted_objects.all():
+        ports = self.fetch_pending(deletion=True)
+        for port in ports:
             self.delete_record(port)
 
     def delete_record(self, port):