test: add unit tests for exec.go file in pkg/utils folder

[Prakhar-Shankar]

What this PR does / why we need it:

This PR adds unit tests for two utility functions in the exec.go file inside the utils package:

• SetExecCommandAttributes
• checkPodStatus

These are pure functions and testable without external dependencies.
This contribution is part of a larger effort to improve test coverage across the utils package.

⚠️ Note: This PR provides partial coverage (currently ~33%) since the Exec() function depends on Kubernetes APIs and remote SPDY execution, which would require more advanced mocking or integration setup. That work can be done in a follow-up PR.

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Fixes #752

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Special notes for your reviewer:

• Tests are written with table-driven and edge case validation
• Maintainers are welcome to suggest how to approach testing Exec() in a future PR (e.g., mocking clients or using fake.Clientset)
• This aligns with LitmusChaos goals of improving code quality and test coverage

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Checklist:

• Fixes Add unit tests for pkg/utils folder #752
• PR message has documentation-related information
• Labelled this PR & related issue with breaking-changes tag (Not applicable)
• PR message has breaking changes related information (N/A)
• Labelled this PR & related issue with requires-upgrade tag (N/A)
• PR message has upgrade related information (N/A)
• Commit has unit tests
• Commit has integration tests (N/A)
• E2E run Required for the changes (N/A)