Adding DeleteResult for volumes.Delete
diff --git a/openstack/blockstorage/v1/volumes/requests_test.go b/openstack/blockstorage/v1/volumes/requests_test.go
index 11b950e..067f89b 100644
--- a/openstack/blockstorage/v1/volumes/requests_test.go
+++ b/openstack/blockstorage/v1/volumes/requests_test.go
@@ -78,8 +78,8 @@
 
 	MockDeleteResponse(t)
 
-	err := Delete(client.ServiceClient(), "d32019d3-bc6e-4319-9c1d-6722fc136a22")
-	th.AssertNoErr(t, err)
+	res := Delete(client.ServiceClient(), "d32019d3-bc6e-4319-9c1d-6722fc136a22")
+	th.AssertNoErr(t, res.Err)
 }
 
 func TestUpdate(t *testing.T) {