rhevh7-install: replaces iptables to firewalld

This patch replaces the enabled service iptables to
firewalld in rhevh7

Change-Id: I4b4324f289b6c2d715f9772a1626666415abb106
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1120562
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>