Use haproxy_bind as override

Haproxy currently forces the binding of external_lb_vip_address
and allows appending additional VIPs such as extra binds and the
internal LB vip. Setting an haproxy_bind list on the service definition
should override, not append, the _bind vips to the service. The service
template offers plenty of other options for appending VIPs.

Change-Id: I2f704e0d36026850857dbb3b9ddee4f64bc07432

releasenotes/notes/haproxy-bind-override-9562bab32b964de2.yaml

@@ -0,0 +1,7 @@
+---
+fixes:
+  - Setting the haproxy_bind list on a service is now used as an override to the
+    other VIPs defined in the environment. Previously it was being treated as
+    an append to the other VIPs so there was no path to override the VIP binds
+    for a service. For example, haproxy_bind could be used to bind a service to
+    the internal VIP only.

templates/service.j2

@@ -19,9 +19,7 @@
 {% endif -%}
 
 {%- if item.service.haproxy_bind is defined %}
-  {% if item.service.haproxy_bind not in vip_binds %}
-    {% set _ = vip_binds.append(item.service.haproxy_bind) %}
-  {% endif %}
+  {% set vip_binds = item.service.haproxy_bind %}
 {% endif -%}
 
 {% for vip_bind in vip_binds %}