Simply looking for the key ID surrounded by spaces in the tested
dnssec-signzone output file is not a precise enough method of checking
for signatures prepared using a given key ID: it can be tripped up by
cross-algorithm key ID collisions and certain low key IDs (e.g. 60, the
TTL specified in bin/tests/system/dnssec/signer/example.db.in), which
triggers false positives for the "dnssec" system test.  Make key ID
extraction precise by using an awk script which operates on specific
fields.