Fix handling of circular MOVED redirects in cluster slot mapping

[barshaul]

Description of change

Circular MOVED responses were incorrectly treated as failover events, causing the
primary node to be demoted and leaving shards with replicas only.

This can occur in DNS-based environments where a MOVED response intentionally
points back to the same address (e.g., MOVED + disconnect to force DNS re-resolution).

This change detects circular MOVED redirects and avoids updating the slot map
when the redirected node is already the shard primary.

Pull Request check-list

Please make sure to review and check all of these items:

• Do tests and lints pass with this change?
• Do the CI tests pass with this change (enable it first in your forked repo and wait for the github action build to finish)?
• Is the new or changed code fully tested?
• Is a documentation update included (if this change modifies existing APIs, or introduces new ones)?
• Is there an example added to the examples folder (if applicable)?

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[petyaslavova]

Hi @barshaul, thank you for your contribution. We will review it soon.