Fix FreeBSD reporting on reruns

Turns out, when your test-suite fails on FreeBSD the rerun logic
would fail as follows:

Results Summary
PASS 1358
FAIL 7
SKIP 47

Running Time: 04:00:02
Percent passed: 96.2%
Log directory: /var/tmp/test_results/20220225T092538
mktemp: illegal option -- p
usage: mktemp [-d] [-q] [-t prefix] [-u] template ...

mktemp [-d] [-q] [-u] -t prefix

mktemp: illegal option -- p
usage: mktemp [-d] [-q] [-t prefix] [-u] template ...

mktemp [-d] [-q] [-u] -t prefix

/usr/local/share/zfs/zfs-tests.sh: cannot create :

No such file or directory

...

This change resolves a flaw from the original commit, 2320e6eb4
("Add zfs-test facility to automatically rerun failing tests")

Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes #13156