Stop firewalld before service iptables and not class firewall

Seems that puppet fails to comprehend that service iptables is from
class firewall and stops firewalld after starting iptables. We solve
this by setting before => Service['iptables']

Change-Id: I964998fe70794efb1d9c7b235a5f1f4aece24aad
Closes-Bug: rhbz#1114121