[9.18] fix: ci: Add ns2/managed1.conf to mkeys extra_artifacts

The ns2/managed1.conf file is created by the setup.sh script. Then, in
the tests.sh script it is moved to ns2/managed.conf. The latter file
name is in mkeys extra_artifacts, but the former one is not. This is a
problem when pytest is started with the --setup-only option as it only
runs the setup.sh script (e.g., in the cross-version-config-tests CI
job) and thus failing the "Unexpected files found" assertion.

Backport of MR !9815

Merge branch 'backport-mnowak/mkeys-add-ns2-managed1-conf-to-extra-artifacts-9.18' into 'bind-9.18'

See merge request isc-projects/bind9!9825