Issue #7449, last part (11): fix many tests if thread support is disabled

 * Use try/except ImportError or test_support.import_module() to import thread
   and threading modules
 * Add @unittest.skipUnless(threading, ...) to testcases using threads
diff --git a/Lib/test/test_httpservers.py b/Lib/test/test_httpservers.py
index e392aee..0dc0a32 100644
--- a/Lib/test/test_httpservers.py
+++ b/Lib/test/test_httpservers.py
@@ -16,10 +16,10 @@
 import urllib
 import httplib
 import tempfile
-import threading
 
 import unittest
 from test import test_support
+threading = test_support.import_module('threading')
 
 
 class NoLogRequestHandler: