Fix idempotence for firewall role

Based on Molecule testing, fix idempotence.

Issue-ID: OOM-1757

Change-Id: Ie2c4cdcf65aeac664d4b76daa7e979f4f23b6bdf
Signed-off-by: Samuli Silvius <s.silvius@partner.samsung.com>
diff --git a/ansible/roles/firewall/tasks/firewall-disable.yml b/ansible/roles/firewall/tasks/firewall-disable.yml
index f406d94..5f1ab53 100644
--- a/ansible/roles/firewall/tasks/firewall-disable.yml
+++ b/ansible/roles/firewall/tasks/firewall-disable.yml
@@ -13,3 +13,4 @@
 - name: Flush iptables
   iptables:
     flush: true
+  changed_when: false  # for idempotence