The code was just wrong. Usually in gitlab-ci, NMTST_SEED_RANDOM is
unset, so the previous code would not have set it. Which means that our
tests run with NMTST_SEED_RANDOM="0".
Fuzzing (or randomizing tests) is very useful, we should do that for the
unit tests that run in gitlab-ci. Fix this.
But don't let the test choose a random number. Instead, let the calling
script choose it. That is, because we might run the tests more than once
(without debugging and no valgrind; in case of failure return with
debugging; with valgrind). Those runs should use the same seed.
This fixes commit 70487d9ff8 ('ci: randomize tests during our CI'),
but as fixing randomization can break previously running tests, we may
only want to backport this commit after careful evaluation.
3bad3f8b24