Implement suport of redis in keystonemiddleware.auth_token #555

Epic #462

As an SCS Developer, I want to use Redis instead of memcache to cache auth tokens.

https://github.com/openstack/keystonemiddleware/blob/master/keystonemiddleware/auth_token/_cache.py

Definition of Ready:

• User Story is small enough to be finished within one sprint
• User Story is clear and understood by the whole team
• Acceptance criteria are defined
• Acceptance criteria are clear and understood by the whole team

Definition of Done:

• All acceptance criteria are met
• Changes have been reviewed
• CI tests have run successfully
• Documentation has been updated
• Release Notes have been updated