request-server: don't return EOF if there is an unexpected error

io.EOF means no error so convert to ErrUnexpectedEOF if we detect
a transfer error

request-server.go

@@ -167,6 +167,9 @@ func (rs *RequestServer) Serve() error {
 	// make sure all open requests are properly closed
 	// (eg. possible on dropped connections, client crashes, etc.)
 	for handle, req := range rs.openRequests {
+		if err == io.EOF {
+			err = io.ErrUnexpectedEOF
+		}
 		req.transferError(err)
 
 		delete(rs.openRequests, handle)