Adjusted the prediff to squash .bad mismatch.
Merge pull request #718 from vasslitvinov/fix-hplx.chpl-prediff

Adjusted the prediff to squash .bad mismatch for hplx.chpl.

For this test:

  test/distributions/dm/hplx.future

the erroneous output can be quite diverse.
I set the prediff - specifically, a case in PREDIFF -
to filter out everything except the correct output
and errors, aiming at a clean match against .bad.

When I did that, I saw "error: attempt to dereference nil"
reported only in ReplicatedDist.chpl, so I filtered
out that error line. Last night we saw that error
reported in ChapelBase.chpl instead. So this change
is to relax the filter to allow that error in any file.