Reset round robin on cluster node RedisURI change

[langchristian96]

Fixes #1909

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[mp911de]

Thanks a lot. The collection size check can happen early on for an early return. We also should consider that the URI of a RedisClusterNode can be null. I'm going to polish up these aspects during the merge.

[mp911de]

Thank you for your contribution. That's merged, polished, and backported now.