objects: minor cleanup in base class
objects: minor cleanup in base class

Some comments from Ia4695b1b10c0370c77b66f31588a56de332f462e were not
addressed in the original patch, but are still worth an effort.

Change-Id: Ibef7adac940b36cc4a4acdf4a80683237e6ec9ae
Partial-bug: #1541928

noironetworks/neutron,bigswitch/neutron,eayunstack/neutron,klmitch/neutron,bigswitch/neutron,openstack/neutron,igor-toga/local-snat,eayunstack/neutron,mahak/neutron,MaximNevrov/neutron,sebrandon1/neutron,klmitch/neutron,cloudbase/neutron,mahak/neutron,openstack/neutron,cloudbase/neutron,openstack/neutron,MaximNevrov/neutron,igor-toga/local-snat,mahak/neutron,noironetworks/neutron,sebrandon1/neutron,huntxu/neutron,huntxu/neutron