isr_admin: Parameterize disk-generation code when creating parcel
isr_admin: Parameterize disk-generation code when creating parcel

- Split MAXKB calculation out of parse_disk_size() into a new function
get_maxkb()

- Rename makeparcel() to new_parcel(), and add a makeparcel() wrapper
function which calls it

- Have new_parcel() take subroutine references for disk size calculation
and chunk generation

- Add makeparcel_gen_chunks() wrapper around gen_chunks() to correctly
permute the argument list passed by new_parcel()

cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr