Clean up network logging and code (#643)

* Apply clippy lints to beacon node

* Remove unnecessary logging and correct formatting

* Apply reviewers suggestions

beacon_node/network/src/message_handler.rs

@@ -1,3 +1,4 @@
+#![allow(clippy::unit_arg)]
 use crate::error;
 use crate::service::NetworkMessage;
 use crate::sync::MessageProcessor;