Refactor TestFernetTokenProvider domain-scoped tests
Refactor TestFernetTokenProvider domain-scoped tests

These tests were not specific to the Fernet provider and they should live in
the general TokenAPITests class so that the behavior is tested against all
token providers.

Subsequent patches will do the same for project-scoped tokens and trust-scoped
tokens.

Change-Id: I3d0bfa5bd9ca1a5d89e5125bed86fe1672f12b39

klmitch/keystone,openstack/keystone,cernops/keystone,mahak/keystone,mahak/keystone,openstack/keystone,klmitch/keystone,rajalokan/keystone,himanshu-setia/keystone,rajalokan/keystone,ilay09/keystone,cernops/keystone,ilay09/keystone,rajalokan/keystone,himanshu-setia/keystone,openstack/keystone,mahak/keystone,ilay09/keystone