[9.20] fix: usr: Fix suppressed missing-glue check in named-checkzone

named-checkzone and named-checkconf -z silently skipped the
missing-glue check for any NS name that had already triggered an
extra-AAAA-glue warning, so zones missing required A glue could pass
validation and be deployed with broken delegations.

Backport of MR !11899

Merge branch 'backport-ondrej/check-tool-err-glue-code-collision-9.20' into 'bind-9.20'

See merge request isc-projects/bind9!11905