message: Update the random seed for one of the sample runs in ex12p.
diff: //
  // Sample runs:
  // mpirun -np 4 ex12p -m ../data/beam-tri.mesh
  -// mpirun -np 4 ex12p -m ../data/beam-quad.mesh
  +// mpirun -np 4 ex12p -m ../data/beam-quad.mesh -s 75
  // mpirun -np 4 ex12p -m ../data/beam-tet.mesh -s 462 -n 10 -o 2 -elast
  // mpirun -np 4 ex12p -m ../data/beam-hex.mesh -s 3878
  // mpirun -np 4 ex12p -m ../data/beam-wedge.mesh -s 81
  