Plane: QLAND if long failsafe on VTOL takeoff

[CallanDaniel]

For QuadPlanes utilizing the RTL_AUTOLAND functionality with DO_LAND_START points and the Q_RTL_MODE parameter set to 0, in order to use a mission-based landing approach:

Presently, if a LONG_FAILSAFE event is triggered during an automated VTOL takeoff, the aircraft will transition back to forward flight regardless of its current altitude, and continue to the waypoint subsequent to the DO_LAND_START command. This behavior presents a significant safety risk, especially for larger aircraft.

This change results in the aircraft entering QLAND mode if a LONG_FAILSAFE is triggered during a VTOL takeoff.

Tested in SITL.

[IamPete1]

Seems sensible.

[IamPete1]

Seems like a good idea. The only edge case I can think if is if your already flying and re-start the mission, in which case we will do the takeoff again but because its not a take off from the ground there is no guarantee that its OK to land at the current location. But we already dump into QLand in VTOL takeoff for timeout or high wind, so that issue exists already.