Relax zone_cdscheck function

Relax zone_cdscheck function

If we have a CDS or CDNSKEY we at least need to have a DNSKEY with the
same algorithm published and signing the CDS RRset. Same for CDNSKEY
of course.

This relaxes the zone_cdscheck function, because before the CDS or
CDNSKEY had to match a DNSKEY, now only the algorithm has to match.

This allows a provider in a multisigner model to update the CDS/CDNSKEY
RRset in the zone that is served by the other provider.

(cherry picked from commit 577bf913b9431c29812b2c7413ecb0dfa1eb7526)