scheduler: Fixed a bug where the bandwidth of reserved cores was not taken into account

[mvegter]

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Description

Testing & Reproduction steps

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Changes to Security Controls

Are there any changes to security controls (access controls, encryption, logging) in this pull request? If so, explain.

[tgross]

@mvegter before you get too much further with this and/or we get into a detailed review, could you help us out by describing the bug in a detail in the PR description?