Fix spurious test failure of test_socket_ssl when run in this order:

  test_codecmaps_tw test_importhooks test_socket_ssl

I don't completely understand the cause, but there's a lot of import magic
going on and this is the smallest change which fixes the problem.

Lib/test/test_importhooks.py

@@ -252,6 +252,10 @@ class ImportHooksTestCase(ImportHooksBaseTestCase):
         for mname in mnames:
             m = __import__(mname, globals(), locals(), ["__dummy__"])
             m.__loader__  # to make sure we actually handled the import
+        # Delete urllib from modules because urlparse was imported above.  
+        # Without this hack, test_socket_ssl fails if run in this order:
+        # regrtest.py test_codecmaps_tw test_importhooks test_socket_ssl
+        del sys.modules['urllib']
 
 def test_main():
     test_support.run_unittest(ImportHooksTestCase)