fix #4072 : minor_version of kubectl calculated by stripping '+' correctly

[ashutosrath]

Pull Request Template

Description

below calculation of minor_version of kubectl corrected. This will work for both macosx bash and other linux bash shells

minor_version=${minor_version::-1}

above code is changed to

minor_version=${minor_version::$((${#minor_version} - 1))}

Fixes: #4072

Type of change

Please delete options that are not relevant.

• 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 not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Checked by running the agent_install.sh script in macosx bash shell

Additional Context (Please include any Screenshots/gifs if relevant)

...

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings
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