Fix iptables service error

Change-Id: I65da02fa835a8436806ab26a4977690fa85e6ded
diff --git a/opencontrail/common.sls b/opencontrail/common.sls
index 42031ce..648db93 100644
--- a/opencontrail/common.sls
+++ b/opencontrail/common.sls
@@ -14,6 +14,7 @@
   service.dead:
   - enable: false
   - name: iptables
+  - onlyif: service iptables status
 
 net.ipv4.ip_forward:
   sysctl.present: