[9.20] fix: nil: Fix parse_dnskey in bin/dnssec/dnssec-ksr.c was failing to reset...

If dns_name_fromtext failed or the subsequent dns_name_compare
failed the lexer's comments state wasn't cleaned up.

Closes #5581

Backport of MR !11109

Merge branch 'backport-5581-parse_dnskey-in-lib-dns-skr-c-was-failing-to-reset-comments-9.20' into 'bind-9.20'

See merge request isc-projects/bind9!11113