Schedule recurring jobs only sidekiq server side

https://github.com/mperham/sidekiq/wiki/Problems-and-Troubleshooting#sidekiq-tries-to-use-a-connection-from-a-child-process-without-reconnecting

Fixes #104
https://github.com/mperham/sidekiq/blob/master/3.0-Upgrade.md

> Client-side middleware should use redis_pool.with { |conn| ... } to perform Redis operations and not Sidekiq.redis.