Reduce the nodelock count for both cache and regular rbtdb

Reduce the nodelock count for both cache and regular rbtdb

Increasing the nodelock count had major impact on the memory footprint
in scenarios where multiple rbtdb structure would be created like
hosting many zones in a single server.

This reverts commit 03446843856a3efbaaec41409b5eea5542501118 and sets
the nodelock count to previously used values.