Adopt to StandardAttribute load method change to "selectin"

Required since the Depends-On patch included, without
it postgres job fails with:-
AttributeError: 'NoneType' object has no attribute 'id'

Depends-On: https://review.opendev.org/c/openstack/neutron-lib/+/923926
Related-Bug: #2072567
Change-Id: I8f2229eb0a9d8dce927ded004037eda93ce3650d
(cherry picked from commit f17cc24)

Author: ralonsoh

neutron/db/db_base_plugin_common.py

@@ -227,10 +227,10 @@ def _make_port_dict(self, port, fields=None,
                         bulk=False):
         if isinstance(port, port_obj.Port):
             port_data = port.db_obj
-            standard_attr_id = port.db_obj.standard_attr.id
+            standard_attr_id = port.db_obj.standard_attr_id
         else:
             port_data = port
-            standard_attr_id = port.standard_attr.id
+            standard_attr_id = port.standard_attr_id
 
         mac = port["mac_address"]
         if isinstance(mac, netaddr.EUI):