Remove service_names hieradata file

The service_names isn't useful anymore:

- hiera('service_names') has been replaced by hiera('enabled_services')
- sensu::subscriptions moved under the {{role.name.lower()}}_extraconfig
  hieradata file.

This is part of the effort which aims to reduce the number of hieradata
files.

Depends-On: I457f2c81a2cf6cc2f42dc4585b41b0d91dacc059
Change-Id: I22081888541e059cd9f258d15990f58df78c38d2
Closes-Bug: #1835551

overcloud.j2.yaml

@@ -978,7 +978,6 @@ resources:
         - config_step
         - {{role.name.lower()}}_extraconfig
         - extraconfig
-        - service_names
         - service_configs
         - cloud_domain
         - bootstrap_node # provided by tripleo-hieradata

puppet/role.role.j2.yaml

@@ -649,12 +649,10 @@ resources:
       value:
         type: json
         datafiles:
-          service_names:
-            service_names: {get_param: ServiceNames}
-            sensu::subscriptions: {get_param: MonitoringSubscriptions}
           service_configs: {get_param: ServiceConfigSettings}
           {{role.name.lower()}}_extraconfig:
             map_merge:
+              - sensu::subscriptions: {get_param: MonitoringSubscriptions}
 {%- if role.deprecated_param_extraconfig is defined %}
               - {get_param: {{role.deprecated_param_extraconfig}}}
 {%- endif %}