+- Only send RADIUS stop record in sessionshutdown when there's an ip address.
+- Reset .die on master takeover (so that dying sessions don't have to
+ hang around until the new master has the same uptime as the old one).
+- Update .last_packet in cluster_handle_bytes only when there have
+ been bytes received from the modem (dead sessions were having the
+ idle timeout reset by stray packets).
+- Use cli_error() for error messages and help.
+- Add a Cisco-Avpair with intercept details to RADIUS Start/Stop
+ records.