Don't exit test_main() with the lock 'done' held -- there's no cleaner

way to guarantee a deadlock on the next call!

If I've inadvertently done some damage to this test, sorry (but I don't
think I have).

Lib/test/test_threaded_import.py

@@ -51,6 +51,7 @@ def test_main():        # magic name!  see above
         done.acquire()
         if verbose:
             print "OK."
+    done.release()
 
 if __name__ == "__main__":
     test_main()