In case if we're migrating to another node where @total_sleep_time
has a big value we might fail here because we don't support tracking
of @total_sleep_time at all, neither we can somehow restore it without
kernel patching (and it's hardly if ever be allowed in vanilla kernel).

Thus simply remember @total_sleep_time value before and after c/r stage
removing it from the computations.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>