Revert "Stop function for debugging purposes"

The functionality for stop() in ost has already been implemented
in init_cl.py (see 2b52357b).

modules/base/pymod/__init__.py

@@ -43,6 +43,3 @@ class StreamLogSink(LogSink):
     self._stream=stream
   def LogMessage(self, message, level):
     self._stream.write(message)
-
-def stop():
-  sys.exit()