ceph grains keyring fixes

Change-Id: I90897170132be46dad2f223d06cc135d329ab8cf
diff --git a/cinder/volume/backend/ceph.yml b/cinder/volume/backend/ceph.yml
index 945f2f9..6b41224 100644
--- a/cinder/volume/backend/ceph.yml
+++ b/cinder/volume/backend/ceph.yml
@@ -1,4 +1,6 @@
 parameters:
+  _param:
+    cinder_storage_client_key: ''
   cinder:
     volume:
       message_queue: