mavproxy always exits with code 1 in non-interactive/daemon mode

[durka]

It looks to me like there is no way to make MAVProxy exit cleanly in non-interactive/daemon mode.

There are only three places I can find a sys.exit(0) in mavproxy.py:

1. If there is a null input passed to process_stdin() (presumably this occurs when the user presses Ctrl-D), not applicable in non-interactive/daemon mode
2. If you pass --version
3. If the signal handler gets called while mavproxy is already attempting to exit, I don't see how to trigger this

At the end of the main function, it always calls sys.exit(1). Am I missing something?