Here is a working method of redirecting any requested HTTP URL to HTTPS in NginX VirtualHosts that handles both HTTP and HTTPS.
For example, to have a single vhost support both HTTP and HTTPS you have normally the following directives:
# Support for HTTP and HTTPS
listen 80;
listen 443 ssl;
ssl_certificate /etc/letsencrypt/live/www.myserver.com/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/www.myserver.com/privkey.pem;
Then to redirect all HTTP requests to HTTPS within this vhost without creating infinite loops you add the following redirect:
if ($scheme != "https") {rewrite ^ https://$host/$request_uri permanent;}
Other methods can be seen here:
http://serverfault.com/questions/67316/in-nginx-how-can-i-rewrite-all-http-requests-to-https-while-maintaining-sub-dom