Bug 29957: Adjust push @$cookie statements in Auth

Bug 29957: Adjust push @$cookie statements in Auth

We can now use $cookie_mgr->replace_in_list instead. This
effectively removes duplicates and keeps the newest cookie.

Note: In the test plan below we are just verifying if
this patch did not change behavior. The replace_in_list
routine has been tested already in a unit test.

Test plan:
Run t/db_dependent/Auth.t
Login at OPAC.
Hit some opac and staff pages.
Perform an Advanced search on OPAC.
Check cookies in browser.
Logout.
Check cookies again. Verify with your do_not_remove_cookie lines
in koha-conf.xml.

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>