Add pod redundancy to Redis

[ancharb]

Describe the task
Build in more redundancy for Redis, which at this point, we believe involves introducing a Helm chart that more easily configure pod redundancy.

Purpose
The OpenShift Silver cluster maintenance often involves draining nodes and rebooting pods. If we don't have redundancy for Redis, our concern is that Redis may experience outages which can have far reaching impacts on the app.

Acceptance Criteria

• make sure we we're not solving a problem that doesn't exist - is Redis as a stateful set already redundant?
• if the above answer is no, then look into deploying Redis with a helm chart
• ensure the redeployed Redis has redundant pods

Additional context

• Tristan: I think I have an answer on our Redis issue, but it's a bit frustrating. It seems like because Redis runs as a stateful set and not a deployment, it takes some more sophisticated orchestration to have replication. For deployments, pods are stateless, so they are interchangeable. You just fire a bunch up, and if one dies, any can take its place, but for stateful sets, the pods all have to talk to each other. Our Redis helm chart doesn't seem to support that. So, we might need to find a new one.