Replaced Mockito.mock by creating actual object

[kanumalivad]

Description

Fixes https://github.com/eclipse-jkube/jkube/issues/3405

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] Feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change
• [ ] Chore (non-breaking change which doesn't affect codebase; test, version modification, documentation, etc.)

Checklist

• [x] I have read the contributing guidelines
• [x] I signed-off my commit with a user that has signed the Eclipse Contributor Agreement
• [x] My code follows the style guidelines of this project
• [x] I Keep It Small and Simple: The smaller the PR is, the easier it is to review and have it merged
• [x] I use conventional commits in my commit messages
• [x] I have performed a self-review of my code
• [ ] I Added CHANGELOG entry
• [ ] I have updated the documentation accordingly
• [ ] No new bugs, code smells, etc. in SonarCloud report
• [ ] 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
• [ ] I tested my code in Kubernetes
• [ ] I tested my code in OpenShift