Confirm iptables service status by checking command status

Currently `upgrades/init.yml` checks iptables status by checking
if `"'Active: active' in service_iptables_status.stdout"` is in
the command output of `systemctl status iptables`. It is not usual and
should be consistent with other codes in the same playbook.

This patch changes iptable service check by command status of
systemctl status iptables.

playbooks/common/openshift-cluster/upgrades/init.yml

@@ -29,8 +29,9 @@
     changed_when: false
     failed_when: false
     register: service_iptables_status
+    check_mode: no
 
   - name: Set fact os_firewall_use_firewalld FALSE for iptables
     set_fact:
       os_firewall_use_firewalld: false
-    when: "'Active: active' in service_iptables_status.stdout"
+    when: service_iptables_status.rc != 0