Fix strange RTL behavior

This commits have fixed #1441 for me. Please review and cross test.

The behaviour should now be:

For COM_DL_LOSS_EN ==0:

- Mission finished, no RC, datalink ok: AUTO_RCRECOVER (RTL)
- Mission finished, no RC, datalink lost: AUTO_RCRECOVER (RTL)

For COM_DL_LOSS_EN == 1:

- Mission finished, no RC, datalink ok: AUTO_MISSION (loitering)
- Mission finished, no RC, datalink lost: AUTO_RCRECOVER (RTL)

I did not follow this one through in detail but it really looks like it was in the wrong place. Did you check if
it makes sense to reset _mission_result.reached = false;` here? Maybe we should move that one to a better location, from the function name it is not obvious that some flags get changed (I think this was mentioned before somewhere maybe...).