Bug 29957: (follow-up) Turn allow list into deny list

Bug 29957: (follow-up) Turn allow list into deny list

See the discussion on the Bugzilla report.
It might be easier to work with a deny list.

Test plan:
Run t/CookieManager.t

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>