Polish create cluster script

[mhmxs]

Small improvements around kubeconfig fetch and renaming management cluster.

General:

• [x] Have you removed all sensitive information, including but not limited to access keys and passwords?
• [x] Have you checked to ensure there aren't other open or closed Pull Requests for the same bug/feature/question?

Pull Request Guidelines:

1. [x] Does your submission pass tests?
2. [ ] Have you added tests?
3. [x] Are you addressing a single feature in this PR?
4. [x] Are your commits atomic, addressing one change per commit?
5. [x] Are you following the conventions of the language?
6. [x] Have you saved your large formatting changes for a different PR, so we can focus on your work?
7. [x] Have you explained your rationale for why this feature is needed?
8. [ ] Have you linked your PR to an open issue