Print out specific filter that failed in object filtering unit test
Print out specific filter that failed in object filtering unit test

This should help in debugging failures. Currently there is no way to
determine which filter failed without putting a breakpoint/printing the
variable.

Change-Id: Ie9bf3b29bc08d9706f1835ca687b90c5909e1610
Partially-Implements: blueprint adopt-oslo-versioned-objects-for-db

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