Bind API service on 0.0.0.0

The API service needs to listen on all IP addresses to allow different
haproxy frontends reach it out.

By default the service binds to 127.0.0.1, and binding it to
options.service_listen_info.watcher_api.ip prevents the assess_status()
code to succeed, this is a common pattern[0]

[0] https://github.com/openstack/charm-neutron-openvswitch/blob/d0731306393840e24e98b52a31977fe16d7aee54/templates/stein/neutron.conf#L14

Change-Id: I3e7b43d0208e251a6b6ab59d0383c989310f2b3b

Author: freyes

src/templates/train/watcher.conf

@@ -1,8 +1,6 @@
 # Train
 [DEFAULT]
 debug = {{ options.debug }}
-bind_host = {{ options.service_listen_info.watcher_api.ip }}
-bind_port = {{ options.service_listen_info.watcher_api.port }}
 host_href = {{ options.external_endpoints.watcher_api.url }}
 
 {% include "parts/section-transport-url" %}
@@ -16,12 +14,12 @@ host_href = {{ options.external_endpoints.watcher_api.url }}
 {% include "parts/section-oslo-middleware" %}
 
 [api]
+# The listen IP address for the watcher API server (host address value)
+host = 0.0.0.0
+
 # The port for the watcher API server (port value)
 port = {{ options.service_listen_info.watcher_api.port }}
 
-# The listen IP address for the watcher API server (host address value)
-host = {{ options.service_listen_info.watcher_api.ip }}
-
 # Number of workers for Watcher API service. The default is equal to the number
 # of CPUs available if that can be determined, else a default worker count of 1
 # is returned. (integer value)