Avoid hanging the test on netbsd5.

Lib/test/test_threading.py

@@ -485,7 +485,8 @@ class ThreadJoinOnShutdown(BaseTestCase):
 
         # Skip platforms with known problems forking from a worker thread.
         # See http://bugs.python.org/issue3863.
-        if sys.platform in ('freebsd4', 'freebsd5', 'freebsd6', 'os2emx'):
+        if sys.platform in ('freebsd4', 'freebsd5', 'freebsd6', 'netbsd5',
+                           'os2emx'):
             raise unittest.SkipTest('due to known OS bugs on ' + sys.platform)
         script = """if 1:
             main_thread = threading.current_thread()