Bug 24144: (bug 23836 follow-up) Fix regressions.t tests

Bug 24144: (bug 23836 follow-up) Fix regressions.t tests

Bug 23836 changes the behavior for tracklinks.pl but did not adjust the
tests.

We must then expect 404 if the pref is turned off.
Also mock_preference cannot work (we are hitting the web server and so
need to set the value in DB and flush the L1 caches)

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Joy Nelson <joy@bywatersolutions.com>
(cherry picked from commit 9cade9186d6234e3ed816e5ab8c32b1060e03341)