Avoid duplicate random ports in tests

Previously, we could have hit cases where we generated the same
listening address twice. Here, we avoid such collisions.

Author: tnull

tests/common/mod.rs

@@ -222,15 +222,14 @@ pub(crate) fn random_port() -> u16 {
 
 pub(crate) fn random_listening_addresses() -> Vec<SocketAddress> {
 	let num_addresses = 2;
-	let mut listening_addresses = Vec::with_capacity(num_addresses);
+	let mut listening_ports = HashSet::with_capacity(num_addresses);
 
-	for _ in 0..num_addresses {
+	while listening_ports.len() < num_addresses {
 		let rand_port = random_port();
-		let address: SocketAddress = format!("127.0.0.1:{}", rand_port).parse().unwrap();
-		listening_addresses.push(address);
+		listening_ports.insert(rand_port);
 	}
 
-	listening_addresses
+	listening_ports.into_iter().map(|p| format!("127.0.0.1:{}", p).parse().unwrap()).collect()
 }
 
 pub(crate) fn random_node_alias() -> Option<NodeAlias> {