Don't overwrite data/checkColliderCorrect.txt on each yade --check

This one is pretty funny. I noticed that checkColliderCorrectness.py was overwriting results data on each run. You forgot to set it back to True after creating the initial data. But git diff would have spotted this anyway in case of problems :)

I noticed this when Anton's yadedaily package failed to overwrite system files on yade --check call ;)