Scary and spammy "error processing request: EOF" logs from TSimpleServer

After upgraded our code to 0.13.0, we noticed a lot of the logs in stderr:

2019/10/22 22:04:52 error processing request: EOF

I think they are generated by this line https://github.com/apache/thrift/blob/v0.13.0/lib/go/thrift/simple_server.go#L167, which means EOF is an error returned by processRequests function.

In that function we actually treat some EOF errors as non-errors (example), so I think it's just that we missed some cases and didn't treat all harmless EOF errors as non-errors.