XFAIL run-pass/task-comm-15 on win32 again

Maybe it works with check-fast, but it stills fails for me

Author: brson

src/test/run-pass/task-comm-15.rs

@@ -1,3 +1,4 @@
+// xfail-win32
 use std;
 import std::comm;
 import std::task;