Redis TLS for coordination in Gnocchi  #651

As an operator, I want be able to use TLS with Gnocchi so that i can use Redis with TLS in my cloud.

Currently, there's an upstream PR covering Redis TLS connectivity.
This PR covers TLS all the services osing Tooz - see #562. However Gnocchi does not use Tooz to communicate with Redis, instead it uses a custom solution. This code does not parse certificates from URL.

This requires an upstream change in Gnocchi repo.

Acceptance criteria:

• Gnocchi is able to use Redis with TLS on.
• Kolla Ansible is able to use Gnocchi with Redis and TLS

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