packaging: firewall: override iptables configuration

Previously iptables configuration was not overridden when the
host was added to the engine.
Now override_iptables is specified when adding the host.
Requiring iptables also on systems with FirewallD because the
engine still doesn't support FirewallD.

Change-Id: I03b0bc75dcbdc92d6f430e3a11d0549a3f0172c0
Bug-Url: https://bugzilla.redhat.com/1014616
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>