Add public config flag that keeps meza from touching haproxy.cfg config

[revansx]

Would like a property to set in /opt/conf-meza/public/public.yml that keeps "meza deploy" from changing anything in the systems current haproxy configuration.

This is needed for sites that have an haproxy config that is significantly different from the one meza deploys. The goal is to be able to run "meza deploy " without any tags and have meza deploy skip the part where the /etc/haproxy/haproxy.cfg file is written.