[radsecproxy] duplicate dynamic discovery

Symptom: radsecproxy is sometimes doing a dynamic discovery (and opens a new tls connection) even if there already is a working (dynamically discovered) connection for the given realm.

Cause: Due to a bug in 'hasdynamicserver()' all information about dynamically discovered realms is removed when any dynamic connection gets closed.

Please review the patch: https://code.nordu.net/?p=user/mauchle/radsecproxy.git;a=commitdiff;h=d768c8...

or pull here: https://git.nordu.net/user/mauchle/radsecproxy.git dup-dyndisc

Best regards, Fabian