When we add DNSKEY records via dynamic update, this should no longer
trigger signing the zone with these keys. This currently happens when
'find_zone_keys()' looks up the keys by inspecting the DNSKEY RRset,
then attempting to read the corresponding key files.
Add checks that inspect the logs whether an attempt to read the key
files for the newly added keys was done (and failed because these files
are not available).
Matthijs Mekking
cda1ae69ac