Version mismatch is now a skippable error

[liztio]

What this PR does / why we need it:

Previously, kubeadm enforced the same major and minor versions as the version of kubernetes it was installing. This is still enforced by default, but now the --force flag can override it. This is useful for testing and other edge cases.

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 #kubeadm/877

Special notes for your reviewer:

Release note:

kubeadm upgrade apply can now ignore version errors with --force

[liztio]

/cc @kubernetes/sig-cluster-lifecycle-pr-reviews

[k8s-ci-robot]

@liztio: The following test failed, say /retest to rerun them all:

Test name	Commit	Details	Rerun command
pull-kubernetes-kubemark-e2e-gce-big	c92aa1a	link	/test pull-kubernetes-kubemark-e2e-gce-big

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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[luxas]

/lgtm

[k8s-github-robot]

/test all [submit-queue is verifying that this PR is safe to merge]

[stealthybox]

Thanks for making this more accommodating for users @liztio 👍
/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: liztio, luxas, stealthybox

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[k8s-github-robot]

[MILESTONENOTIFIER] Milestone Pull Request: Up-to-date for process

@liztio @luxas @stealthybox

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[k8s-github-robot]

Automatic merge from submit-queue (batch tested with PRs 64605, 64570). If you want to cherry-pick this change to another branch, please follow the instructions here.