Currenty a parent can go far away from child and we will need to wait
too long for checking results.

This pach limits delta to [MIN_DELTA, 2 * MIN_DELTA].

Thi patch should fix current errors for the CRIU-iter job in Jenkins.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>