auth_request called multiple times for same single request

[garyc]

Thanks for the warning! I have to admit i was a little surprised to learn
that, arguably, the two major browsers don't implement 100-continue and have
no plan to do so. I know our scenario is far from typical but POST uploads
are surely widespread.

Thanks to all for your help on this, the support provided by this forum is
really great and much appreciated.

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,276512,276594#msg-276594