Insert hints as non-auth into cache, so info received from the net is

Insert hints as non-auth into cache, so info received from the net is
recorded in the cache.

Also make sure the root NS refresh happens more often if max-cache-ttl is low.
This is needed as the records no longer maintain the 1000 hours TTL.
In the existing setup, a reprime (with potential outdated info) was done at that
point in time since all root-server address records would expire at the same
time.

Lastly, fix a infinite (caught by depth check) recursion in getBestNSFromCache().

Fixes #10177.