test: add UT for filewatcher

[Zhupku]

This pull request includes changes to improve the handling of program termination and adds a test for the WatchFileForChanges function. The most important changes include the introduction of a separate exit function and the addition of a comprehensive test for file watching.

Improvements to program termination handling:

• pkg/filewatcher/filewatcher.go: Introduced a separate exit function to handle program termination, replacing direct calls to os.Exit with this function. [1] [2]

Addition of tests:

• pkg/filewatcher/filewatcher_test.go: Added a new test for the WatchFileForChanges function, including a mock exit function to capture exit codes and simulate file changes.<!-- Thanks for sending a pull request! Here are some tips for you:

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What type of PR is this?

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #

Requirements:

• uses conventional commit messages
• includes documentation
• adds unit tests
• tested upgrade from previous version

Special notes for your reviewer:

Release note:

none

[k8s-ci-robot]

Hi @Zhupku. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[andyzhangx]

/ok-to-test

[k8s-ci-robot]

@Zhupku: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-azuredisk-csi-driver-external-e2e-single-az	4a1375f	link	true	/test pull-azuredisk-csi-driver-external-e2e-single-az

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository. I understand the commands that are listed here.

[Zhupku]

/retest

[andyzhangx]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: andyzhangx, Zhupku

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Needs approval from an approver in each of these files:

• OWNERS [andyzhangx]

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