phaul: use relative path for parent link
phaul: use relative path for parent link

Absolute paths for parent links may not work on restore.
e.g: restore on a different server(during migration).

See https://github.com/checkpoint-restore/criu/blob/criu-2.x-stable/criu/image.c#L432

Signed-off-by: Jacob Wen <7568f2e94ed170d8618606da6292179f0e1b678f@oracle.com>
Signed-off-by: Andrei Vagin <74c05afa918858348d6db8037d82fa8124870113@virtuozzo.com>

checkpoint-restore/go-criu,checkpoint-restore/go-criu,checkpoint-restore/go-criu