Fix upload test on OpenSpeedTest with uhttpd (OpenWRT)

ost-upload

#!/bin/sh
# this file: /www/cgi-bin/ost-upload
# Change index.html (in openspeedtest directory) like this:
#     var openSpeedTestServerList = [
#        {"ServerName":"Home", "Download":"downloading", "Upload":"/cgi-bin/ost-upload", "ServerIcon":"DefaultIcon"}
# Plus make this file executable in /www/cgi-bin

cat >/dev/null # read all the data
# sure, whatever....
printf "Status: 200 OK\r\n"
printf "Content-Type: application/octet-stream\r\n"
printf "Content-Length: 0\r\n"
printf "Cache-Control: no-store\r\n"
printf "\r\n"