When the sample is removed we need to decrease sample cache usage,
even when capacity is set to zero.
Otherwise we're getting wrong usage after capacity is changed.
Change-Id: I38820c0f9441abec3086189698ec5a904e1e9b6f Reviewed-by: Ling Hu <ling.hu@nokia.com> Reviewed-by: Michael Goddard <michael.goddard@nokia.com>