Skip previous version validation in CI

[razo7]

Why we need this PR

Should fix an error when VERSION equals CI_VERSION, so it would skip the previous version validation in CI

Error in post-submit automation

make[1]: Entering directory '/home/go/src/github.com/medik8s/node-maintenance-operator'
924
Error: PREVIOUS_VERSION must be set for the selected VERSION
VERSION equals CI_VERSION,

Changes made

Modify the verify-previous-version target so it fails when VERSION doesn't equal CI_VERSION.
Similar to SNR PR

[openshift-ci]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[razo7]

The PR is not affecting the code, but rather the GitHub CI so no need to set the PR as draft

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: clobrano, razo7

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• OWNERS [clobrano,razo7]

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[razo7]

/cherry-pick release-0.17

[openshift-cherrypick-robot]

@razo7: new pull request created: #125

In response to this:

/cherry-pick release-0.17

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