Use a ten second timeout for join requests

[twz123]

Description

This prevents k0s from hanging on idle network connections, such as random glitches, badly behaving load balancers, and so on.

Add a context to the JoinClient methods and call them with a context that times out after 10 seconds when joining a controller. This has the side effect that joining will also be interruptible by SIGTERM and Ctrl+C.

Fixes #4557.

Type of change

• [x] 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)
• [ ] Documentation update

How Has This Been Tested?

• [x] Manual test
• [x] Auto test added

Checklist:

• [x] My code follows the style guidelines of this project
• [x] My commit messages are signed-off
• [x] 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
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [ ] Any dependent changes have been merged and published in downstream modules
• [x] I have checked my code and corrected any misspellings