Add default domain to fixture.v3.V3FederationToken
Add default domain to fixture.v3.V3FederationToken

Each ephemeral user is by default a member of service domain called
"Federated". We should reflect this in fixture.v3.V3FederationToken as
well.

Change-Id: I46a68048c4520e8bace4800b7635df3f8d351dd0

citrix-openstack-build/keystoneauth,jamielennox/keystoneauth,sileht/keystoneauth