Periodic FSM vacuum doesn't happen in one-pass strategy vacuum.

Hi,

With commit c120550edb86, If we got the cleanup lock on the page,
lazy_scan_prune() marks dead item IDs directly to LP_UNUSED. So the
following check with has_lpdead_items made the periodic FSM vacuum in
the one-pass strategy vacuum no longer being triggered:

            if (got_cleanup_lock && vacrel->nindexes == 0 && has_lpdead_items &&
                blkno - next_fsm_block_to_vacuum >= VACUUM_FSM_EVERY_PAGES)
            {
                FreeSpaceMapVacuumRange(vacrel->rel, next_fsm_block_to_vacuum,
                                        blkno);
                next_fsm_block_to_vacuum = blkno;
            }

Before c120550edb86, since we marked dead item IDs to LP_DEAD once
even in the one-pass strategy vacuum, we used to call
lazy_vacuum_heap_page() to vacuum the page and to call
FreeSpaceMapVacuum() periodically, so we had that check.

I've attached a patch to fix it.

Regards,

-- 
Masahiko Sawada
Amazon Web Services: https://aws.amazon.com