Update kubernetes/zulip-rc.yml with memcached and Redis authentication

[andersk]

Split from #232.

[ilanpillemer]

I assume this is why its failing for me? Only when this step is done will the k8s config work?

[andersk]

I would expect the k8s config to still work, just without memcached and Redis authentication, like before. generate_secrets doesn’t attempt to automatically turn on authentication unless the memcached and Redis servers are 127.0.0.1.