ci(preparations): disable IPv6 for the Ubuntu-18.04 test setup

unbound/_test_dependencies.sls

@@ -1,6 +1,16 @@
-{%- if grains['os'] == 'Ubuntu' %}
+{%- if grains['os'] == 'Ubuntu' or grains['os_family'] == 'Arch' %}
 unbound-_test_dependencies-stop-systemd-resolved:
   service.dead:
     - name: systemd-resolved
     - enable: False
 {%- endif %}
+
+{%- if grains.get('osfinger', '') == 'Ubuntu-18.04' %}
+unbound-_test_dependencies-no-ipv6:
+  cmd.run:
+    - name: 'echo "  do-ip6: no" >> /etc/unbound/unbound.conf'
+    - require:
+      - file: unbound-config-file-file-managed
+    - require_in:
+      - service: unbound-service-running-service-running
+{%- endif %}