Set policy_file in the oslo_policy group

policy_file in DEFAULT is deprecated

Change-Id: I6698a810d5e6c395a18aed8066e61f8c4bae2408
diff --git a/lib/ceilometer b/lib/ceilometer
index 3a4a4fb..9abdbfe 100644
--- a/lib/ceilometer
+++ b/lib/ceilometer
@@ -195,7 +195,7 @@
 
     # Install the policy file for the API server
     cp $CEILOMETER_DIR/etc/ceilometer/policy.json $CEILOMETER_CONF_DIR
-    iniset $CEILOMETER_CONF DEFAULT policy_file $CEILOMETER_CONF_DIR/policy.json
+    iniset $CEILOMETER_CONF oslo_policy policy_file $CEILOMETER_CONF_DIR/policy.json
 
     cp $CEILOMETER_DIR/etc/ceilometer/pipeline.yaml $CEILOMETER_CONF_DIR
     cp $CEILOMETER_DIR/etc/ceilometer/event_pipeline.yaml $CEILOMETER_CONF_DIR