fix in list instead of dictionary
diff --git a/metadata/service/volume/single.yml b/metadata/service/volume/single.yml
index 8a95e20..881d579 100644
--- a/metadata/service/volume/single.yml
+++ b/metadata/service/volume/single.yml
@@ -31,5 +31,4 @@
         user: openstack
         password: ${_param:rabbitmq_openstack_password}
         virtual_host: '/openstack'
-        ha_queues: true
-      backend: []
\ No newline at end of file
+        ha_queues: true
\ No newline at end of file