We ignored errors for simple syntax in `PortOpt` (missed that in the previous migration of this code). This make sure we don't ignore `nat.Parse` errors. Test has been migrate too (errors are not exactly the same as before though -_-) Signed-off-by: Vincent Demeester <vincent@sbr.pm> Upstream-commit: aa4ecd153b88644a53b23b7c46332d9b50007930 Component: engine