Prevent haproxy to run iptables during docker-puppet configuration

Prevent haproxy to run iptables during docker-puppet configuration

When docker-puppet runs module tripleo::haproxy to generate haproxy
configuration file, and tripleo::firewall::manage_firewall is true,
iptables is called to set up firewall rules for the proxied services
and fails due to lack of NET_ADMIN capability.

Make the generation of firewall rule configurable by exposing a
new argument to the puppet module. That way, firewall management can
be temporarily disabled when being run through docker-puppet.

Change-Id: I2d6274d061039a9793ad162ed8e750bd87bf71e9
Partial-Bug: #1697921