lujfsd

ignore join_multcast_v4 error. fix issue https://github.com/jhelovuo/RustDDS/issues/208#issue-1291111797

我有一个网卡，给了两个IP地址，如下图：  在第二个网卡(eth0:1)加入组播时，加入失败，返回错误。why not continue? ``` for multicast_if_ipaddr in get_local_multicast_ip_addrs()? { match multicast_if_ipaddr { IpAddr::V4(a) => { mio_socket.join_multicast_v4(&multicast_group, &a)?; } IpAddr::V6(_a) => error!("UDPListener::new_multicast() not implemented for IpV6"), // TODO }...

The func ```BIT_STRING__compactify``` called at ```BIT_STRING_encode_uper``` BIT_STRING__compactify will remove the trailing 0-bits from the given bit string，this is why?