refactor test_catalog
refactor test_catalog

- Tests for "missing" attributes are actually testing with null values,
  not missing keys.
- Not being able to explicitly provide alternative URLs resulting in
  hacky workarounds that can be avoiding by simply exposing kwargs with
  reasonable defaults
- Several tests redundantly asserted the expected response status, which
  is already handled by the test framework

Change-Id: Icadb4927bcf03ca7e79fef1507e419a4932f32a9
Related-Bug: 1250765

mahak/keystone,roopali8/keystone,rushiagr/keystone,cernops/keystone,nuxeh/keystone,jumpstarter-io/keystone,dims/keystone,dstanek/keystone,rajalokan/keystone,nuxeh/keystone,derekchiang/keystone,ajayaa/keystone,vivekdhayaal/keystone,cernops/keystone,takeshineshiro/keystone,dsiddharth/access-keys,jonnary/keystone,openstack/keystone,derekchiang/keystone,maestro-hybrid-cloud/keystone,promptworks/keystone,dims/keystone,promptworks/keystone,mahak/keystone,ging/keystone,openstack/keystone,himanshu-setia/keystone,nuxeh/keystone,UTSA-ICS/keystone-kerberos,klmitch/keystone,reeshupatel/demo,jamielennox/keystone,vivekdhayaal/keystone,himanshu-setia/keystone,promptworks/keystone,JioCloud/keystone,vivekdhayaal/keystone,reeshupatel/demo,dstanek/keystone,jonnary/keystone,jamielennox/keystone,rodrigods/keystone,blueboxgroup/keystone,ging/keystone,ilay09/keystone,blueboxgroup/keystone,idjaw/keystone,MaheshIBM/keystone,ilay09/keystone,jumpstarter-io/keystone,takeshineshiro/keystone,UTSA-ICS/keystone-kerberos,rushiagr/keystone,openstack/keystone,rodrigods/keystone,rajalokan/keystone,JioCloud/keystone,mahak/keystone,roopali8/keystone,rajalokan/keystone,MaheshIBM/keystone,dsiddharth/access-keys,reeshupatel/demo,ilay09/keystone,jumpstarter-io/keystone,dsiddharth/access-keys,dstanek/keystone,klmitch/keystone,ajayaa/keystone,derekchiang/keystone,rushiagr/keystone,maestro-hybrid-cloud/keystone,idjaw/keystone