fix commander: set _was_landed before _land_detector topic update

Before _was_landed was set to the same value as the current
_land_detector.landed, thus outside of the update condition,
_was_landed && !_land_detector.landed could never be true.

This affects setting the home position, which is now set upon arming AND
upon takeoff.

src/modules/commander/Commander.hpp

@@ -362,7 +362,6 @@ private:
 	bool		_status_changed{true};
 	bool		_arm_tune_played{false};
 	bool		_was_landed{true};
-	bool		_was_falling{false};
 	bool		_was_armed{false};
 	bool		_failsafe_old{false};	///< check which state machines for changes, clear "changed" flag
 	bool		_have_taken_off_since_arming{false};