Change HTTP methods for OpenStack CDN
diff --git a/openstack/cdn/v1/serviceassets/requests.go b/openstack/cdn/v1/serviceassets/requests.go
index 0a5b073..1ddc65f 100644
--- a/openstack/cdn/v1/serviceassets/requests.go
+++ b/openstack/cdn/v1/serviceassets/requests.go
@@ -43,6 +43,6 @@
 	}
 
 	var res DeleteResult
-	_, res.Err = c.Request("DELETE", url, gophercloud.RequestOpts{})
+	_, res.Err = c.Delete(url, nil)
 	return res
 }