Revert "remove a random test in batList taking too long", and use Vincent Hugo's advice instead.

When a random test takes too long to run, the solution is not to
remove it but reduce the number of time it is run:

  (*$Q nsplit & ~count:10
    ...
  *)

This means that any eventual bug will not be found each time the tests
are run (and may take a large number of individual attempts to
be hit), but it's indeed much better than having no test at all.