Fix feature flags for some tests files

The test util module requires both the "os-poll" and "net" features.

tests/aio.rs

@@ -1,5 +1,5 @@
-#![cfg(feature = "os-poll")]
 #![cfg(any(target_os = "freebsd", target_os = "dragonfly"))]
+#![cfg(all(feature = "os-poll", feature = "net"))]
 
 use mio::{event::Source, Events, Interest, Poll, Registry, Token};
 use std::{

tests/unix_pipe.rs

@@ -1,4 +1,4 @@
-#![cfg(all(unix, feature = "os-poll", feature = "os-ext"))]
+#![cfg(all(unix, feature = "os-poll", feature = "os-ext", feature = "net"))]
 
 use std::io::{Read, Write};
 use std::process::{Command, Stdio};

tests/util/mod.rs

@@ -1,6 +1,6 @@
 // Not all functions are used by all tests.
 #![allow(dead_code, unused_macros)]
-#![cfg(any(feature = "os-poll", feature = "net"))]
+#![cfg(all(feature = "os-poll", feature = "net"))]
 
 use std::mem::size_of;
 use std::net::SocketAddr;

tests/waker.rs

@@ -1,4 +1,4 @@
-#![cfg(feature = "os-poll")]
+#![cfg(all(feature = "os-poll", feature = "net"))]
 
 use mio::{Events, Poll, Token, Waker};
 use std::sync::{Arc, Barrier};