client: Centralize parcel.cfg parsing
client: Centralize parcel.cfg parsing

- Always parse parcel.cfg during startup if we have it.  This saves the
individual modes from having to do this explicitly.  Modes which fetch
the parcel.cfg as part of their operation still need to call
parse_parcelcfg() themselves.

- Have parse_parcelcfg() write directly to %cfg

- Don't unlink parcel.cfg on parse_parcelcfg() failure

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