remove unused import

darcs-hash:20090310152346-b2873-dda4df2423c85afc19746dec18adc725ac3c840c
msrp_send_message.py: use explicit terminate() instead of GreenEngine.shutdown()

darcs-hash:20090310152403-b2873-defb4160dbc7249e46d40647d6786eb14bf55536