add tests for helm utils

[nitishkumar71]

Description

Add tests for helm utils

Motivation and Context

• [x] I have raised an issue to propose this change, which has been given a label of design/approved by a maintainer (required) Closes #986

How Has This Been Tested?

If updating or adding a new CLI to arkade get, run:

go build && ./hack/test-tool.sh TOOL_NAME

NA. As it's logic tests included , so nothing additional tests are needed to be done.

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Documentation

• [ ] I have updated the list of tools in README.md if (required) with ./arkade get --format markdown
• [ ] I have updated the list of apps in README.md if (required) with ./arkade install --help

Checklist:

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [x] I've read the CONTRIBUTION guide
• [x] I have signed-off my commits with git commit -s

• [ ] I have tested this on arm, or have added code to prevent deployment