criu: don't return negative values from main() 2/2

We should return 1 not -1, because -1 becomes 255.

This is second part, patching return from functions.
Using 'ret != 0' condition seems like the best and easiest
thing to do, so we expect a function to return 0 in normal
case and any non-zero value in case of error.

Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>