perf: lessen reload frequency to mitigate load of servers

[supercaracal]

The following commands are slow query.

• https://redis.io/docs/latest/commands/cluster-nodes/
• https://redis.io/docs/latest/commands/cluster-slots/
• https://redis.io/docs/latest/commands/cluster-shards/

So clients should care about load of servers.

• Redis OSS cluster client discovery and exponential backoff

This pull request mitigates it. The following issue is related.

• Client is raising Redis::Cluster::NodeMightBeDown when Redis Cluster is observed to be healthy #368