Make some fixes to eviction dirty count validation routine.
Replace __evict_dirty_validate with a check during shutdown.  Change __evict_dump_cache into a function to be called from a debugger.
Ensure eviction dirty tracking accounts for root pages.

Root pages can be marked as dirty, but discarded without writing changes.
Merge pull request #501 from wiredtiger/lsm-ckpt-evict-dirty

Make some fixes to eviction dirty count validation routine.