multiple frontend mode: avoid unnecesary slurmd configuration warning

When running in multiple-slurmd mode, the actual hardware configuration reported
by the slurmd is ignored, and internal entries (via register_front_ends() just
use 1 as dummy value for CPUs, sockets, cores, and threads.

On a dual-core service node this lead to continual warning messages like

[2011-04-01T10:06:40] Node configuration differs from hardware
   Procs=1:2(hw) Sockets=1:1(hw)
   CoresPerSocket=1:2(hw) ThreadsPerCore=1:1(hw)
[2011-04-01T10:07:24] Node configuration differs from hardware
   Procs=1:2(hw) Sockets=1:1(hw)
   CoresPerSocket=1:2(hw) ThreadsPerCore=1:1(hw)