Avoid publishing on the Redis channel if there are no other subscribers

[davidjrh]

In order to avoid unnecessary calls to the Redis server on single server scenarios, would be nice to don't publish the notification message on the Redis channel as there are no servers subscribed other than the current one. This add unnecessary overhead.

[davidjrh]

Thinking about this now, publishing on single server scenarios is still good. For example, on Application Restart events, it is faster to get the items from the Redis Cache than calculating them again connecting to the database.

Closing the issue.