isr_admin: Create new parcel.cfg files with mode 600
isr_admin: Create new parcel.cfg files with mode 600

- In "isr_admin addparcel", create the new parcel.cfg with mode 600 and
its containing directory with mode 700.  If the user's account was created
with "isr_admin adduser", its home directory will already be mode 700, but
it doesn't hurt to be careful.

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