Addressed m-lammps.valgrind timeout in nightly.
... and removed .valgrind.timeout
Merge pull request #883 from vasslitvinov/fix--m-lammps.valgrind--timeout

Addressed m-lammps.valgrind timeout in nightly.

* By reducing the number of atoms from 3200 to 320.

* I hope 320 atoms are likely to exercise the same code paths as 3200 atoms.

* Changed a couple of consts in the source to be 'config const'.
  I am using only one - I changed the others just in case for the future.

* Added .execopts to specify the number of atoms.

* The input file, ljcut.in, is unchanged, the remaining atoms in it
  will be unused for valgrind runs.

* Adjusted .good based on what the program is producing today
  for this number of atoms.
  (I do not know how to verify correctness of this output.)

* The large timeout we had for valgrind should no longer be needed
  - the test ran in 23 seconds on my machine - so I am removed the .timeout.

Recall that m-lammps.valgrind.chpl is a symlink to m-lammps.chpl.
I introduced it earlier so that we can have different settings
for valgrind than for correctness testing.