disable request body buffering for file upload

[garyc]

Please ignore the last message, having learned a bit more about probing the
file system we can now see that it is PHP that is caching the file to the
system default location (hence rootfs) a small change to the PHP
configuration has sorted this.

Thanks to everyone for your help

Gary

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,275567,276162#msg-276162