blocking detection manager fails after setting acceleration.

I was debugging `strat_autopos()` and I got the following bug : If I changed the acceleration at the end of the function using `traj_set_acc` for some reason the blocking detection manager would refuse to allow the robot to do any movement.
Removing the call to `traj_set_acc` removed the problem and I have no time to investigate it at the moment, so i am opening this issue to remember it.
