Spindump should recognise failed version negotiations attempts

[jariarkko]

Test case trace_quic_v25_ngx for instance is one such case.

(But can we theoretically recognise these? Unclear)

[MaximProshin]

According to the quic transport draft version 25 a server responds by the Version Negotiation packet if a client selected an unsupported version. The client then must abandon the current connection attempt and may initiate a new connection using one of the versions supported by the server. From that I understood that the spindump tool just needs to recognize the Version Negotiation packet, report the version negotiation fail if needed and close the connection.
One corner case here is that a server may decide to not send the Version Negotiation packet (or it might be lost) but it seems to be more general problem for the spindump tool.