Fix TcpStream::local_addr example code

The local address's port is not 8080 in this example, that's the remote peer address port. On my machine, the local address is different every time, so I've changed `assert_eq` to only test the IP address

src/libstd/net/tcp.rs

@@ -198,8 +198,8 @@ impl TcpStream {
     ///
     /// let stream = TcpStream::connect("127.0.0.1:8080")
     ///                        .expect("Couldn't connect to the server...");
-    /// assert_eq!(stream.local_addr().unwrap(),
-    ///            SocketAddr::V4(SocketAddrV4::new(Ipv4Addr::new(127, 0, 0, 1), 8080)));
+    /// assert_eq!(stream.local_addr().unwrap().ip(),
+    ///            IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)));
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn local_addr(&self) -> io::Result<SocketAddr> {