tests: ignore minor 'recheck' regression for BSD make

tests: ignore minor 'recheck' regression for BSD make

It turns out that, with NetBSD 5.1 make and FreeBSD 9 make, running
"make recheck" two times in a row quickly fails to correctly re-run
the failed tests in the second run.

That issue has been introduced likely introduced in commit
'v1.12.1-95-gd5443e4' of 20102-07-01, "parallel-tests: reimplement
fix for bug#11791".

Anyway, the use case that has been broken is not realistic (who is
going to run "make recheck" two times in one second, without modifying
any of the tests or the tested programs in the meantime?), so we believe
the best fix is to simply work around the issue in the affected test
cases, rather than risking to slow down or uglify the 'recheck' rule.

* t/parallel-tests9.sh: Enhance a little.
* t/tap-recheck.sh: Adjust adding proper '$sleep' calls were required.
* t/parallel-tests-log-override-recheck.sh: Likewise.
* t/test-driver-custom-multitest-recheck.sh: Likewise.
* t/test-driver-custom-multitest-recheck2.sh: Likewise.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>