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_threading.py b/Lib/test/test_threading.py
index 70dd026..2e2558a 100644
--- a/Lib/test/test_threading.py
+++ b/Lib/test/test_threading.py
@@ -5,8 +5,8 @@
 import random
 import re
 import sys
-import threading
-import thread
+thread = test.test_support.import_module('thread')
+threading = test.test_support.import_module('threading')
 import time
 import unittest
 import weakref