fix(agent): remove reconnection delay on DuplicateServerError

[IvanHunters]

Description

This PR fixes a regression in v0.33.0 where agents fail to reconnect after connection loss, leaving Kubernetes nodes in permanent NotReady state.

Problem

In v0.33.0, when DuplicateServerError occurs during reconnection with clientsCount < serverCount, the code adds a ~1s delay:

} else {
    backoff = cs.resetBackoff()
    duration = wait.Jitter(backoff.Duration, backoff.Jitter)  // ~1s delay
}

Since newAgentClient() uses DNS load balancing, it connects to a random proxy pod. When a client disconnects, the reconnection attempt has only ~20% chance (1/5 pods) of selecting the correct pod. Wrong selections trigger DuplicateServerError, and the 1s delay significantly slows reconnection.

Impact: Average reconnection time increases from ~500ms to ~5s per client. With multiple simultaneous disconnects (e.g., VM restart), cascading failures prevent full recovery.

Solution

Remove the else block that adds delay. Let duration remain 0 (default value), enabling immediate retry through time.Sleep(0). This allows fast reconnection via DNS load balancing without creating a tight loop (the loop already includes gRPC dial time and network round trips).

Context

The release-0.33 branch already contains one fix from v0.34.0 (moving lastReceivedServerCount update to after successful AddClient()). This PR adds the second critical fix - removing the delay on reconnection attempts.

Together, these changes restore the fast reconnection behavior from v0.28.6 and align with the complete fix in v0.34.0.

Testing

Verified in production cluster:

• Before fix: Nodes remain NotReady permanently after VM restart (v0.33.0)
• After fix: Expected behavior matches v0.34.0 - agents reconnect within seconds

Related: #816

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[k8s-ci-robot]

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[k8s-ci-robot]

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[cheftako]

/ok-to-test

[cheftako]

This has potential negative impact if something else is going on and now we generate a ton of connection requests. Happy to have this added as an option but I think it would be safer to add a flag for this behavior. We should also default to the existing behavior so we are backward compatible.

[cheftako]

/ok-to-test

[cheftako]

Can you rebase on the latest?
Also the PR cannot be merged until you sign the CLA