Fix blacklistd's state restoral at startup

The blacklistd daemon attempted to restore the filtering rules
before the database of blocked addresses was opened, so no rules
were being reloaded. Now the rules are properly recreated when the
daemon is started with '-r'.

This bug was fixed locally, and then sent upstream to NetBSD.
This changeset is the import the NetBSD version of the change,
which added debugging output to alert about a null database.

Reviewed by: emaste
Obtained from: NetBSD
MFC after: 1 week
Sponsored by: The FreeBSD Foundation