This change populates testsuite.log with unit test errors.
This is the most important output that we need to show.
But it is hidden now.

errors.log is not created, it is seldom useful.
To make errors.log usefull, we would need to capture
stdout and errout interleaved into errors.log
and keep stdout on standard output.
If we want such a logic, it belongs somewhere into unit test framework.
We have more tests than `dsstest`.