TCP tracing may ignore some incoming ICMP responses

[fujiapple852]

This method will eagerly evaluate both self.recv_tcp_sockets() and self.recv_icmp_probe() and will discard the result of the latter if the former is Some:

    fn recv_probe(&mut self) -> TraceResult<Option<ProbeResponse>> {
        match self.protocol {
            TracerProtocol::Icmp | TracerProtocol::Udp => self.recv_icmp_probe(),
            TracerProtocol::Tcp => Ok(self.recv_tcp_sockets()?.or(self.recv_icmp_probe()?)),
        }
    }

This could, in rare cases for TCP tracing, lead to ICMP response packets being ignored.