Handle Max/GrpCPU limits better

This code was originally put here to enforce checks to make sure jobs
didn't go over the limit.  If they didn't request the amount then we set
the limit and worked off that as if it were a request.

If we do this now we could get jobs deigned which would cancel the job at
submit with a very unrelated note as to why the job failed.

Since we now check this these limits after the node selection this isn't
needed.