Don't send client parameters in delete message.

This avoids a race condition since the delete messages are sent
asynchronously.

diskwriter/diskwriter.go

@@ -75,7 +75,7 @@ func (client *Client) Status() map[string]interface{} {
 	return nil
 }
 
-func (client *Client) PushClient(id, username string, permissions group.ClientPermissions, status map[string]interface{}, kind string) error {
+func (client *Client) PushClient(id, username string, permissions *group.ClientPermissions, status map[string]interface{}, kind string) error {
 	return nil
 }