[backport] perf: dhcp err msg in network swiftv2 code path (#3793)

[isaac-dasan]

• fix: dhcp error message to include kubelet err msg
• Update network/secondary_endpoint_client_linux.go

Reason for Change:

Requirements:

• uses conventional commit messages
• includes documentation
• adds unit tests
• relevant PR labels added

Notes:

[Copilot]

Pull Request Overview

This PR backports a fix to include the kubelet network-not-ready message in the DHCP error path and adds a unit test for that failure.

• Include kubelet.NetworkNotReadyErrorMsg in the wrapped DHCP error
• Add a mock DHCP failure client and test case to verify the new error message
• Import required packages (context, errors, kubelet) in the test

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
network/secondary_endpoint_client_linux.go	Wrap DHCP discovery errors with the kubelet error message
network/secondary_endpoint_linux_test.go	Add mock DHCP failure and test case to assert error

Comments suppressed due to low confidence (3)

network/secondary_endpoint_linux_test.go:401

• The test only asserts the kubelet error substring; consider also verifying that the wrapped error includes the underlying DHCP failure message (mock DHCP discover request failed) for more thorough coverage.

			wantErrMsg: kubelet.NetworkNotReadyErrorMsg,

network/secondary_endpoint_client_linux.go:19

• The errorSecondaryEndpointClient variable is declared but never used; consider removing it to reduce dead code and confusion.

var errorSecondaryEndpointClient = errors.New("SecondaryEndpointClient Error")

network/secondary_endpoint_linux_test.go:18

• [nitpick] Importing the internal kubelet package in tests may introduce fragility if that package path changes; consider copying the constant or defining a local alias to decouple from kubelet internals.

	"k8s.io/kubernetes/pkg/kubelet"

[isaac-dasan]

/azp run Azure Container Networking PR

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[sheylatrudo]

Just a minor nit. Otherwise looks good.