A failure during "make test" should be signalled to the caller by means of
a non-zero exit code. Without that signal, it's very hard to run the
regression test suite in an automated fashion.

> git-annex used to have a Makefile that ignored make test exit status,
> but that was fixed in commit dab5bddc64ab4ad479a1104748c15d194e138847,
> in October 6th. [[done]] --[[Joey]] 
