tempest/test.py: make set_validation_resources() more idiomatic
tempest/test.py: make set_validation_resources() more idiomatic

It's a cosmetic change but it shouldn't be controversial.

Change-Id: Ia02844319565eebea92ed8b0628dea37bdd22063

Juniper/tempest,masayukig/tempest,vedujoshi/tempest,cisco-openstack/tempest,masayukig/tempest,cisco-openstack/tempest,openstack/tempest,openstack/tempest,vedujoshi/tempest,Juniper/tempest