Comment 4 for bug 1799454

same with one of the serviceinstance deletion
10/23/2018 09:20:32 AM [cvm] [CRITICAL]:
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/cvm/__main__.py", line 182, in <module>
    main(parsed_args)
  File "/usr/lib/python2.7/site-packages/cvm/__main__.py", line 169, in main
    vmware_monitor.sync()
  File "/usr/lib/python2.7/site-packages/cvm/monitors.py", line 7, in sync
    self._controller.sync()
  File "/usr/lib/python2.7/site-packages/cvm/controllers.py", line 24, in sync
    self._vmi_service.sync_vmis()
  File "/usr/lib/python2.7/site-packages/cvm/services.py", line 39, in sync_vmis
    self._delete_unused_vmis()
  File "/usr/lib/python2.7/site-packages/cvm/services.py", line 131, in _delete_unused_vmis
    self._vnc_api_client.delete_vmi(vnc_vmi.get_uuid())
  File "/usr/lib/python2.7/site-packages/cvm/clients.py", line 393, in delete_vmi
    self.delete_instance_ip(instance_ip_ref.get('uuid'))
  File "/usr/lib/python2.7/site-packages/cvm/clients.py", line 506, in delete_instance_ip
    self.vnc_lib.instance_ip_delete(id=uuid)
  File "/usr/lib/python2.7/site-packages/vnc_api/vnc_api.py", line 51, in wrapper
    return func(self, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/vnc_api/vnc_api.py", line 805, in _object_delete
    self._request_server(OP_DELETE, uri)
  File "/usr/lib/python2.7/site-packages/vnc_api/vnc_api.py", line 1032, in _request_server
    retry_after_authn=retry_after_authn, retry_count=retry_count)
  File "/usr/lib/python2.7/site-packages/vnc_api/vnc_api.py", line 1091, in _request
    raise RefsExistError(content)
RefsExistError: Delete when resource still referred: ['http://10.204.217.140:8082/service-instance/15013bc4-9c48-4db4-bb41-4115a4639ccc']