Bug 14121: Silence warnings t/db_dependent/Auth_with_cas.t

Bug 14121: Silence warnings t/db_dependent/Auth_with_cas.t

TEST PLAN
---------
1) $ prove t/db_dependent/Auth_with_cas.t
   -- CGI security warning
2) apply patch
3) $ prove t/db_dependent/Auth_with_cas.t
   -- no noise.
4) koha qa test tools

Signed-off-by: Nick Clemens <nick@quecheelibrary.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Not able to reproduce the error on my setup, but the code
is a clear improvement over the previous version.
Signed-off-by: Tomas Cohen Arazi <tomascohen@unc.edu.ar>