message: action: don't change yaw when landing
  This should fix the issue where the vehicle turns to face North when
  trying to land which is unnecessary and confusing.
diff: @@ -136,6 +136,7 @@ ActionResult ActionImpl::land() const
  MAVLinkCommands::CommandLong command{};
  command.command = MAV_CMD_NAV_LAND;
  + command.params.param4 = NAN; // Don't change yaw.
  command.target_component_id = _parent->get_autopilot_id();
  return action_result_from_command_result(_parent->send_command(command));
  @@ -355,6 +356,7 @@ void ActionImpl::land_async(const Action::result_callback_t &callback)
  MAVLinkCommands::CommandLong command{};
  command.command = MAV_CMD_NAV_LAND;
  + command.params.param4 = NAN; // Don't change yaw.
  command.target_component_id = _parent->get_autopilot_id();
  _parent->send_command_async(command,
  