storagenode/nodestats: Add sat to heldamount error

Nodes are receiving an error that heldamount rpc doesn't exist on a
satellite. This simply adds which satellite to the error.

Change-Id: I7708e0511b55fdd2425969db2a545645339bad81

storagenode/nodestats/cache.go

@@ -205,6 +205,7 @@ func (cache *Cache) CacheHeldAmount(ctx context.Context) (err error) {
 				return nil
 			}
 
+			cache.log.Error("heldamount err", zap.String("satellite", satellite.String()))
 			return err
 		}