Fix test

Author: newpavlov

tests/pass/shims/fs.rs

@@ -342,7 +342,7 @@ fn test_pread_pwrite() {
 
     // Ensure that cursor position is not changed
     f.read_exact(&mut buf1).unwrap();
-    assert_eq!(&buf2, b"  m");
+    assert_eq!(&buf1, b"  m");
 
     Ok(())
 }