pfsync: Fix state sync during initial bulk update
States learned via pfsync from a peer with the same ruleset checksum were not
getting assigned to rules like they should because pfsync_in_upd() wasn't
passing the PFSYNC_SI_CKSUM flag along to pfsync_state_import.
Submitted by: Kajetan Staszkiewicz <vegeta tuxpowered.net>
Obtained from: OpenBSD
Sponsored by: InnoGames GmbH