distro/tests: fix file permissions set by ansible

Ansible switched default file perm to 600 from more permissive 666. Add file mode explicitly to avoid issues.

distro/tests/ansible-roles/knot_dns/tasks/configure_zone.yaml

@@ -2,6 +2,7 @@
 - name: create example.com zone
   copy:
     dest: /etc/knot/example.com.zone
+    mode: 0644
     content: |
       $ORIGIN example.com.
       $TTL 3600