test() - Added unit tests for util/executables.go.

[yuvraj-kolkar17]

Description

This PR adds unit tests for the functions in util/executables.go.

Part of the issue #46

How Has This Been Tested?

go test ./util -coverprofile=coverage.out   

github.com/kubeslice/kubeslice-cli/util 3.227s  coverage: 50.0% of statements 

Checklist:

• The title of the PR states what changed and the related issues number (used for the release note).
• Does this PR requires documentation updates?
• I've updated documentation as required by this PR.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have tested it for all user roles.
• I have added all the required unit test cases.

Does this PR introduce a breaking change?

[yuvraj-kolkar17]

PTAL @priyank-upadhyay @narmidm @Rahul-D78 @gourishkb