Previous version would require plugin to override all the
isFooFlightMode methods to work correctly. Now just change mode name
and regular plugin code works correctly.

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

before, with a version of eg. 1.5.0, the user was wrongly notified.

Firmware plugin: Sequence guided mode correctly, widen modes in which guided support should be available

* Remove leftover debugging message
* Fix segfault on Linux at close for #3164