Bug 12887: User logged out on refresh after CAS authentication

Bug 12887: User logged out on refresh after CAS authentication

If the user is already logged-in, do not trigger CAS authentication
even if there is a ticket in the parameters.

1) Authenticate to the OPAC through CAS.
2) Once redirected to your account, hit F5 or the refresh button of your browser.
3) You're logged out.

Signed-off-by: Koha Team Lyon 3 <koha@univ-lyon3.fr>
Signed-off-by: Luce Barbey <luce.barbey@cirad.fr>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Added sign of lines according to bug.
Works as described, small change.

Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>