make logging rely on a single SG index

roles/openshift_logging_elasticsearch/templates/elasticsearch.yml.j2

@@ -52,7 +52,7 @@ path:
 searchguard:
   authcz.admin_dn:
   - CN=system.admin,OU=OpenShift,O=Logging
-  config_index_name: ".searchguard.${DC_NAME}"
+  config_index_name: ".searchguard"
   ssl:
     transport:
       enabled: true