fix: avoid creation of VirtualNode if ResourceSlice deleting

[fra98]

Description

This PR fixes a bug where the virtualnode resource was created even when the owner resourceslice was deleting.
This fix helps deleting the offloading when using GitOps tools like ArgoCD.

[adamjensenbot]

Hi @fra98. Thanks for your PR!

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[fra98]

/rebase test=true

[fra98]

/rebase test=true

[fra98]

/rebase test=true

[fra98]

/merge