Function custom_cgroup_affinity_change 

pub fn custom_cgroup_affinity_change(ctx: &Ctx<'_>) -> Result<AssertResult>

Two cgroups with worker affinities randomized four times during the run. Each randomization assigns half the available CPUs to each worker.

Both cgroups persist on the Backdrop so every SetAffinity op in the four randomization Steps finds the same live workers.