Captive portal: fix per-user session timeouts
Captive portal: fix per-user session timeouts

Don't overwrite the global session timeout value with a user's radius-provided timeout
that would then be reused in the same run for users without a custom session timeout.

NewEraCracker/pfsense,pfsense/pfsense,dennypage/pfsense,NewEraCracker/pfsense,dennypage/pfsense,dennypage/pfsense,phil-davis/pfsense,pfsense/pfsense,dennypage/pfsense,pfsense/pfsense,pfsense/pfsense,phil-davis/pfsense,phil-davis/pfsense,phil-davis/pfsense,NewEraCracker/pfsense,NewEraCracker/pfsense