[PATCH] fix oops in updating thread cputime and task time

[Fawzi Mohamed]

We have a machine with a (back ported) fix working without problems since a few days.
We don´t consider it
	tested-by: Thomas Dargel <td@xxxxxxxxxxxxxxxxxxxx>
because last time it did need 19 days of computation to happen, but it should be fixed.

Fawzi and Thomas.