How to disallow scheduling of task on client unless explicitly told to

I’d like to run Docker tasks on my Nomad cluster servers for monitoring. However, I would like all my tasks by default not to run on these nodes unless explicitly configured to. Is there any way to configure this kind of behavior?

Relevant GitHub issue: [Feature] Ability to have nodes which can be used only for job with specific constraint. · Issue #2299 · hashicorp/nomad · GitHub