Fix for magneto fix that still kept hanging sometimes

Plz Wait till 20141210 before (maybe) honoring pull request, needs re-test with current master, maybe the other code "MAXRETRY etc". made it anyhow work 100%. Will be tested 5 different ARdrone2 with a good history of flying and misuse.
> 60hours of statistical experience of ARdrone in ON state. Also based on a remark of a developer from Parrot and the debugging done by CDW.