rwhod: react to audit pam events to broadcast updates

Listen to read-only audit packets from the kernel to react on user
logins/logouts. This way, we can immediately notify other machines on
the network whenever there is a change to the user session list.

src/server/rwhod.rs

@@ -1,8 +1,10 @@
+mod audit_watcher;
 mod packet_receiver;
 mod packet_sender;
 mod rwhod_status;
 mod status_registry;
 
+pub use audit_watcher::audit_change_notifier;
 pub use packet_receiver::rwhod_packet_receiver_task;
 pub use packet_sender::{determine_relevant_interfaces, rwhod_packet_sender_task};
 pub use rwhod_status::{generate_rwhod_status_update, generate_rwhod_user_entries};