kube-master-installation: improve systemd cross-unit robustness.

[jkh52]

Also some minor reliability tweaks.

What type of PR is this?

/kind bug

What this PR does / why we need it:

We have seen sometimes that if metadata service is flaky and kube-master-installation unit fails, downstream may still try and fail (such as kube-master-configuration). Our normal health signal based repair waits a very long time, so you can have a failed but idle master node for some time.

This adds more clear dependency between units, and immediately reboots the machine if kube-master-installation.service fails (much faster than otherwise).

Which issue(s) this PR fixes:

Special notes for your reviewer:

Does this PR introduce a user-facing change?

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

NONE

[k8s-ci-robot]

Hi @jkh52. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[jkh52]

/assign @wojtek-t

(similar to #101015)

[jkh52]

/retest

[k8s-ci-robot]

@jkh52: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

In response to this:

/retest

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[zmerlynn]

/hold

I have concerns (raised internally).

[jkh52]

Latest snapshot removes the reboot (there are some cons) and vastly increases the retry interval.

[zmerlynn]

/unhold

[zmerlynn]

/ok-to-test
/lgtm

[wojtek-t]

/approve

/retest

/triage accepted

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jkh52, wojtek-t

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