This is an addition to commit 6273a5c ("Add ability to restore with
missing sysctls on the target node").

travis-ci: success for Document --weak-syscalls
Cc: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Acked-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>