fix wrong namespace in template file

Change-Id: Ie932ed8dcaaf943521fa3eae4ce9b3abee9c4a90
diff --git a/ceilometer/files/liberty/ceilometer-server.conf.Debian b/ceilometer/files/liberty/ceilometer-server.conf.Debian
index ea1dbde..199d62d 100644
--- a/ceilometer/files/liberty/ceilometer-server.conf.Debian
+++ b/ceilometer/files/liberty/ceilometer-server.conf.Debian
@@ -625,7 +625,7 @@
 # Region name to use for OpenStack service endpoints. (string
 # value)
 #os_region_name=<None>
-os_region_name={{ agent.get('region', 'RegionOne') }}
+os_region_name={{ server.get('region', 'RegionOne') }}
 
 # Type of endpoint in Identity service catalog to use for
 # communication with OpenStack services. (string value)