Deal with EINTR in net timeout tests

We've seen sporadic QE failures in the timeout tests on this assertion:

    assert!(kind == ErrorKind::WouldBlock || kind == ErrorKind::TimedOut);

So there's an error, but not either of the expected kinds.  Adding a
format to show the kind revealed `ErrorKind::Interrupted` (`EINTR`).

For the cases that were using `read`, we can just use `read_exact` to
keep trying after interruption.  For those using `recv_from`, we have to
manually loop until we get a non-interrupted result.

src/libstd/net/tcp.rs

@@ -1548,8 +1548,9 @@ mod tests {
 
         let mut buf = [0; 10];
         let start = Instant::now();
-        let kind = stream.read(&mut buf).err().expect("expected error").kind();
-        assert!(kind == ErrorKind::WouldBlock || kind == ErrorKind::TimedOut);
+        let kind = stream.read_exact(&mut buf).err().expect("expected error").kind();
+        assert!(kind == ErrorKind::WouldBlock || kind == ErrorKind::TimedOut,
+                "unexpected_error: {:?}", kind);
         assert!(start.elapsed() > Duration::from_millis(400));
         drop(listener);
     }
@@ -1570,8 +1571,9 @@ mod tests {
         assert_eq!(b"hello world", &buf[..]);
 
         let start = Instant::now();
-        let kind = stream.read(&mut buf).err().expect("expected error").kind();
-        assert!(kind == ErrorKind::WouldBlock || kind == ErrorKind::TimedOut);
+        let kind = stream.read_exact(&mut buf).err().expect("expected error").kind();
+        assert!(kind == ErrorKind::WouldBlock || kind == ErrorKind::TimedOut,
+                "unexpected_error: {:?}", kind);
         assert!(start.elapsed() > Duration::from_millis(400));
         drop(listener);
     }

src/libstd/net/udp.rs

@@ -1030,8 +1030,14 @@ mod tests {
         let mut buf = [0; 10];
 
         let start = Instant::now();
-        let kind = stream.recv_from(&mut buf).err().expect("expected error").kind();
-        assert!(kind == ErrorKind::WouldBlock || kind == ErrorKind::TimedOut);
+        loop {
+            let kind = stream.recv_from(&mut buf).err().expect("expected error").kind();
+            if kind != ErrorKind::Interrupted {
+                assert!(kind == ErrorKind::WouldBlock || kind == ErrorKind::TimedOut,
+                        "unexpected_error: {:?}", kind);
+                break;
+            }
+        }
         assert!(start.elapsed() > Duration::from_millis(400));
     }
 
@@ -1049,8 +1055,14 @@ mod tests {
         assert_eq!(b"hello world", &buf[..]);
 
         let start = Instant::now();
-        let kind = stream.recv_from(&mut buf).err().expect("expected error").kind();
-        assert!(kind == ErrorKind::WouldBlock || kind == ErrorKind::TimedOut);
+        loop {
+            let kind = stream.recv_from(&mut buf).err().expect("expected error").kind();
+            if kind != ErrorKind::Interrupted {
+                assert!(kind == ErrorKind::WouldBlock || kind == ErrorKind::TimedOut,
+                        "unexpected_error: {:?}", kind);
+                break;
+            }
+        }
         assert!(start.elapsed() > Duration::from_millis(400));
     }
 

src/libstd/sys/unix/ext/net.rs

@@ -1654,8 +1654,9 @@ mod test {
         or_panic!(stream.set_read_timeout(Some(Duration::from_millis(1000))));
 
         let mut buf = [0; 10];
-        let kind = stream.read(&mut buf).err().expect("expected error").kind();
-        assert!(kind == io::ErrorKind::WouldBlock || kind == io::ErrorKind::TimedOut);
+        let kind = stream.read_exact(&mut buf).err().expect("expected error").kind();
+        assert!(kind == ErrorKind::WouldBlock || kind == ErrorKind::TimedOut,
+                "unexpected_error: {:?}", kind);
     }
 
     #[test]
@@ -1675,8 +1676,9 @@ mod test {
         or_panic!(stream.read(&mut buf));
         assert_eq!(b"hello world", &buf[..]);
 
-        let kind = stream.read(&mut buf).err().expect("expected error").kind();
-        assert!(kind == io::ErrorKind::WouldBlock || kind == io::ErrorKind::TimedOut);
+        let kind = stream.read_exact(&mut buf).err().expect("expected error").kind();
+        assert!(kind == ErrorKind::WouldBlock || kind == ErrorKind::TimedOut,
+                "unexpected_error: {:?}", kind);
     }
 
     // Ensure the `set_read_timeout` and `set_write_timeout` calls return errors