Improve performance of dhcp integration client processing

[bdraco]

Proposed change

We were using run_callback_threadsafe here which has the overhead of creating a future and waiting for the result when we throw it away. We shouldn't use this helper unless we need to wait for the result. There are other places in the codebase that currently do this that I will audit and adjust in future PRs

Noticed this while working on #105884

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• Dependency upgrade
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• This PR fixes or closes issue: fixes #
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[jpbede]

Looks good, nice catch @bdraco 👍

[bdraco]

thanks