Resize zone mem/task pools when processing catalog zones, if necessary

named creates pre-defined amount of zone task, zone-load task, and memory context pools on startup, calculated for operating with 1000 or less zones. Then named can quickly increase that number (if necessary) when loading the configuration, based on the actual number of the loaded zones. The number also may be auto-adjusted (only increased) during each reconfiguration.

Since catalog zone update can introduce a large amount of new zones, it makes sense to adjust this number (if necessary) also when processing catalog zones.