Upload tests report no results when run against non-Linux NDT server

[nosnilmot]

Upload tests with ndt-server running on non-Linux (darwin) do not report any results:

$ ~/go/bin/ndt7-client -scheme wss -server 172.26.0.65:4443 -upload=true -download=false -no-verify
upload in progress with 172.26.0.65

upload: complete

Test results

    Server: 172.26.0.65
    Client: 172.26.0.65

              Upload
     Throughput:     0.0 
        Latency:     0.0 

I believe this is because ndt-server on non-Linux does not provide TCPInfo and PR #75 changed ndt7-client-go to require server-side TCPInfo for upload test results. It would be nice if there could be a fallback to client-side AppInfo in this case.