Active item update after maintenance can take long time

After maintenance without data collection ends nextcheck is recalculated for host items having type Zabbix agent (active). This update is done by iterating through all items (as there are not host->items[] index) and can lock the configuration cache for significant time.

This was done to avoid active items from showing up in queue after maintenance. But rather than recalculating nextcheck for active items we can apply host and item data_expected_from fields when calculating queue.