Clean omitted files from system tests

Clean omitted files from system tests

Any CI job:
- I:dns64:file ns1/Ksigned.+005+*.key not removed
- I:dns64:file ns1/Ksigned.ns1/Ksigned.+005+*.private
- I:dns64:file ns1/Ksigned.ns1/Ksigned.+005+*.key
- I:dns64:file ns1/Ksigned.ns1/Ksigned.+005+*.private
- I:dns64:file ns1/Ksigned.ns1/dsset-signed.
- I:dns64:file ns1/Ksigned.ns1/named.conf
- I:dns64:file ns1/Ksigned.ns1/signed.db
- I:dns64:file ns1/Ksigned.ns1/signed.db.signed
- I:dns64:file ns1/Ksigned.ns2/named.conf
- I:ixfr:file ns5/named.run.prev not removed
- I:legacy:file ns1/named_dump.db.test20 not removed

(cherry picked from commit 14a104d1211611aa0d5465bd339a7d4c711acf33)