Add None value to service.description attribute
Add None value to service.description attribute

When using kolla_keystone_service module, if
description attribute is not created(example Keystone).
Service update will fail due missing attribute.

This change adds a None value to description in order to
allow service update when description was not added.

Change-Id: I568db4559428525ac6c5083cfc20cffc20be6342

openstack/kolla,rahulunair/kolla,stackforge/kolla,coolsvap/kolla,GalenMa/kolla,nihilifer/kolla,intel-onp/kolla,rahulunair/kolla,stackforge/kolla,mrangana/kolla,stackforge/kolla,openstack/kolla,intel-onp/kolla,nihilifer/kolla,GalenMa/kolla,mrangana/kolla,coolsvap/kolla,coolsvap/kolla