Use signer name when disabling DNSSEC algorithms

Use signer name when disabling DNSSEC algorithms

When disabling algorithms, use the signer name to determine if the
algorithm is disabled or not.  This allows for algorithms to be
cleanly disabled on a zone level basis.  Previously, just using the
records owner name, "disable-algorithms" could impact resolution of
names that where not disabled.  This does now mean that
"disable-algorithms" can not be used to disable part of a zone anymore.