Cleanup docstrings in test_v3_federation.py
Cleanup docstrings in test_v3_federation.py

This is a non-functional change that cleans up some nits with respect to
docstrings for test cases.

Change-Id: I4c0d631bd53783a7cd0a2b413da87a77640fb665

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