Refactor deprecations tests
Refactor deprecations tests

- rename to make the name reveal the test's intentions
- simplify the implementation

Change-Id: I52ee09f15130e15e25dd6e64bfdee1f480dbc6ed

klmitch/keystone,takeshineshiro/keystone,idjaw/keystone,rajalokan/keystone,vivekdhayaal/keystone,roopali8/keystone,vivekdhayaal/keystone,openstack/keystone,openstack/keystone,takeshineshiro/keystone,ajayaa/keystone,jonnary/keystone,himanshu-setia/keystone,dstanek/keystone,klmitch/keystone,mahak/keystone,roopali8/keystone,maestro-hybrid-cloud/keystone,dims/keystone,jamielennox/keystone,openstack/keystone,vivekdhayaal/keystone,maestro-hybrid-cloud/keystone,mahak/keystone,cernops/keystone,ilay09/keystone,jonnary/keystone,rajalokan/keystone,dstanek/keystone,mahak/keystone,rajalokan/keystone,ajayaa/keystone,cernops/keystone,ilay09/keystone,ilay09/keystone,himanshu-setia/keystone,idjaw/keystone,dstanek/keystone,jamielennox/keystone,dims/keystone