In some user scenarious (like implementing DNS RR) it might be useful to
bind on 0.0.0.0 but at the same time do not conflict with other services
that are binded to the same ports. For that, we can specify a specific
interface, on which haproxy will be binded to 0.0.0.0.
In netstat it would be represented like `0.0.0.0%br-mgmt:5000`.
With that we also allow to fully override `vip_binds` if assumtions
that role make are not valid for some reason.
Change-Id: Ic4c58ef53abc5f454b6fbebbd87292a932d173ae
901523ddbb