Weather vane working inconsistently

[xdwgood]

Describe the bug
Through simulation in gazebo, I found that the vane will work in LAND and RTL mode only after I have performed the mission task. If I do not execute the mission mode, the vane in land and rtl mode will never work

To Reproduce
Steps to reproduce the behavior:

1. Fetch latest master branch
   2.Add debug code PX4_INFO("1111") here: https://github.com/PX4/Firmware/blob/master/src/lib/flight_tasks/tasks/Auto/FlightTaskAuto.cpp#L249
2. run make px4_sitl_default gazebo_tailsitter
3. Execute one-click take-off command by QGC
4. switch land mode by QGC
   5.No debug output 1111 during landing
   6.Execute one-click take-off command by QGC
   7.Execute survey mission command by QGC
   8.switch position mode by QGC
   9.switch Land/RTL mode by QGC
   10.debug output 1111 during landing/rtl

Expected behavior
For me: I want the vane algorithm to work properly in LAND and RTL mode, and don’t rely on whether I have ever performed a mission(survey)

EDIT On the other hand: If we only want to activate the weather vane function under the mission task, we can add pos_sp_triplet-> current.allow_weather_vane = false after the mission is completed. But I prefer the weather vane to work in land and RTL

Source of the problem
This problem is caused by:
This （_sub_triplet_setpoint.get().current.allow_weather_vane）condition is true only when the mission task is executed. here: https://github.com/PX4/Firmware/blob/master/src/modules/navigator/mission.cpp#L692

Possible related links:
#10883

[xdwgood]

I solved this problem by adding pos_sp_triplet-> current.allow_weather_vane = true in LAND and RTL;

Can we make allow_weather_vane default to true?
FYI： @sfuhrer

[xdwgood]

fix by #13761