test: Ignore a deadlocking test on OSX

This test apparently keeps making no progress and timing out builds on the OSX
builder, so this commit is switching the test to be ignored.

cc rust-lang#16872

Author: alexcrichton

src/test/run-pass/tcp-accept-stress.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-macos #16872 spurious deadlock
+
 #![feature(phase)]
 
 #[phase(plugin)]