fix pipeline steps that require fibermap to be sorted by FIBER

Some pipeline steps apparently make the assumption that `fibermap_row_index = FIBER%500` which is a fragile assumption. I've fixed that in a few places in desispec and desisim branches newfibermap, but I haven't found all cases. I don't have specific enough symptoms to know where without further debugging, thus this ticket. I have good redshift efficiency if the fibermap is sorted but terrible efficiency if it isn't, and it might be due to sky subtraction. TDB.

In the meantime desihub/fiberassign#147 restores the sorted order so that we can proceed with the pipeline testing.