changing to k8s cluster sets cores to empty

[johrstrom]

When you change from a SLURM cluster to a k8s cluster the # of cores gets set to empty. This is likely because we try to set the mins and maxes based on data-ppn-CLUSTER attributes and there are none for kubernetes and clamp it (i.e., you had the max on pitzer, 48, switch to owens so the value get's set to 28, the max owens).