Don't clone before borrowing

Clippy told us to change function parameters to references, but
wasn't able to then tell us that the clone() before borrowing
was superfluous. This patch removes those by hand.

No expectation of a performance improvement here, since we were
just cloning reference counts. Just removes a bunch of noise.

src/bin/client-demo.rs

@@ -224,7 +224,7 @@ fn main() {
 
     let signal = Arc::new(AtomicBool::new(false));
     let mut c_threads = vec![];
-    let validators = converge(&leader, &signal.clone(), num_nodes, &mut c_threads);
+    let validators = converge(&leader, &signal, num_nodes, &mut c_threads);
     assert_eq!(validators.len(), num_nodes);
 
     let mut client = mk_client(&leader);
@@ -395,7 +395,7 @@ fn converge(
     let window = default_window();
     let gossip_send_socket = udp_random_bind(8000, 10000, 5).unwrap();
     let ncp = Ncp::new(
-        &spy_ref.clone(),
+        &spy_ref,
         window.clone(),
         spy_gossip,
         gossip_send_socket,