CORD-3143 Set port.service_instance

Change-Id: Iea4c91dd19a48745aa5b5051f82be77588667a87
diff --git a/xos/synchronizer/pull_steps/pull_ports.py b/xos/synchronizer/pull_steps/pull_ports.py
index 425d3eb..656cd6b 100644
--- a/xos/synchronizer/pull_steps/pull_ports.py
+++ b/xos/synchronizer/pull_steps/pull_ports.py
@@ -89,6 +89,7 @@
                         instance=None, # TODO(smbaker): link to openstack instance
                         ip=ip,
                         mac=mac,
-                        port_id=os_port.id)
+                        port_id=os_port.id,
+                        service_instance=instance)
             port.save()
             log.info("Created port", port=port, os_port=os_port)