✨ Improve tests on conditions and reasons for hcloud machine server with hcloud mock

[aniruddha2000]

What this PR does / why we need it:

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #943

Special notes for your reviewer:

Please confirm that if this PR changes any image versions, then that's the sole change this PR makes.

TODOs:

• squash commits
• include documentation
• add unit tests

[guettli]

@aniruddha2000 this PR is open since several months. What do you think: are you able to finish it during the next weeks, or is it better to close the PR?

[janiskemper]

if we close it then we'll lose it right? I'd like to keep the code but this is certainly not the highest prio right now @guettli

[guettli]

if we close it then we'll lose it right? I'd like to keep the code but this is certainly not the highest prio right now @guettli

No, the changes are not lost. I close it now. We can start again from here.