adjust RR-dumping style a little

adjust RR-dumping style a little

The former "default" dumping style isn't really used anywhere in Knot.
The only visible difference is that RRSIGs are now logged *without*
replacing their TTLs by the original non-decremented TTL values.
That can avoid some confusion when reading debug logs.
(Those original TTLs are still shown a bit further on each line.)