Comment 2 for bug 1691786

I think it caused by the port which changes from None ==> <Port>

May 19 13:35:23 ubuntu heat-engine[23204]: ResourceDefinition(u'instancegovmain-', u'OS::Nova::Server', properties={u'flavor': u'm1.tiny', u'image': u'cirros-0.3.5-x86_64-disk', u'networks': [{u'port': None}]}, metadata=None, depends=None, deletion_policy=None, update_policy=None, condition=None)

May 19 13:35:23 ubuntu heat-engine[23204]: ResourceDefinition(u'instancegovmain-', u'OS::Nova::Server', properties={u'flavor': u'm1.tiny', u'image': u'cirros-0.3.5-x86_64-disk', u'networks': [{u'port': u'6a6f820d-257a-48e6-bc91-86bda848aceb'}]}, metadata=None, depends=None, deletion_policy=None, update_policy=None, condition=None)

Notice the port got some id. Hence showing as updated.