Fix undercarriage icon staying up while wheels being lowered

When pressing F7 with the undercarriage up, to lower it, the icon flashes to a down arrow and then goes back to an up arrow again until the undercarriage is fully deployed. Fixed by setting the icon to down while it is being lowered too, which required querying the transition status.
Autopilot undercarriage sound fix

When the autopilot sets the undercarriage down, it calls SetWheelState(true) in every frame, which causes the undercarriage sound to be triggered repeatedly until it is fully deployed. Fixed by not considering SetWheelState to succeed if the transition value doesn't change.
Cleaner way to do the same
Merge remote-tracking branch 'pgimeno/undercarriage'