Combine the functionality of test_support.run_unittest()

and test_support.run_classtests() into run_unittest()
and use it wherever possible.

Also don't use "from test.test_support import ...", but
"from test import test_support" in a few spots.

From SF patch #662807.

Lib/test/test_shutil.py

@@ -14,15 +14,9 @@ class TestShutil(unittest.TestCase):
 
 
 
-def suite():
-    suite = unittest.TestSuite()
-    suite.addTest(unittest.makeSuite(TestShutil))
-    return suite
-
-
 def test_main():
-    test_support.run_suite(suite())
+    test_support.run_unittest(TestShutil)
 
 
 if __name__ == '__main__':
-    unittest.main(defaultTest='suite')
+    test_main()