Prevent shutdown ordering crashes

_finalize methods need information which is not available if all you
have is a mavlink_message_t

- Now responds to request_list using a worker routine to send out
params one at a time
- Support for failure modes for unit testing

- Delay gps position for better testing
- Longer delay on home position

This mechanism automatically queues data into the correct thread where necessary, otherwise the method is invoked directly with low overhead.

At the same time remove the UDP socket event workaround. It is not a problem.

Plus other auto connect bug fixes