Corrected X-Forwarded-Proto nginx settings for sandboxes

This commit properly sets the X-Forwarded-Proto header so Django knows when a request originated as HTTPS.

 ECOM-2835

playbooks/roles/course_discovery/templates/edx/app/nginx/sites-available/course_discovery.j2

@@ -49,9 +49,15 @@ server {
   {% endif %}
 
   location @proxy_to_app {
+    {% if NGINX_SET_X_FORWARDED_HEADERS %}
+    proxy_set_header X-Forwarded-Proto $scheme;
+    proxy_set_header X-Forwarded-Port $server_port;
+    proxy_set_header X-Forwarded-For $remote_addr;
+    {% else %}
     proxy_set_header X-Forwarded-Proto $http_x_forwarded_proto;
     proxy_set_header X-Forwarded-Port $http_x_forwarded_port;
     proxy_set_header X-Forwarded-For $http_x_forwarded_for;
+    {% endif %}
     proxy_set_header Host $http_host;
 
     proxy_redirect off;

playbooks/roles/nginx/templates/edx/app/nginx/sites-available/credentials.j2

@@ -44,9 +44,15 @@ server {
   {% include "robots.j2" %}
 
 location @proxy_to_app {
+    {% if NGINX_SET_X_FORWARDED_HEADERS %}
+    proxy_set_header X-Forwarded-Proto $scheme;
+    proxy_set_header X-Forwarded-Port $server_port;
+    proxy_set_header X-Forwarded-For $remote_addr;
+    {% else %}
     proxy_set_header X-Forwarded-Proto $http_x_forwarded_proto;
     proxy_set_header X-Forwarded-Port $http_x_forwarded_port;
     proxy_set_header X-Forwarded-For $http_x_forwarded_for;
+    {% endif %}
     proxy_set_header Host $http_host;
 
     proxy_redirect off;

playbooks/roles/nginx/templates/edx/app/nginx/sites-available/programs.j2

@@ -78,9 +78,15 @@ server {
   {% include "robots.j2" %}
 
 location @proxy_to_app {
+    {% if NGINX_SET_X_FORWARDED_HEADERS %}
+    proxy_set_header X-Forwarded-Proto $scheme;
+    proxy_set_header X-Forwarded-Port $server_port;
+    proxy_set_header X-Forwarded-For $remote_addr;
+    {% else %}
     proxy_set_header X-Forwarded-Proto $http_x_forwarded_proto;
     proxy_set_header X-Forwarded-Port $http_x_forwarded_port;
     proxy_set_header X-Forwarded-For $http_x_forwarded_for;
+    {% endif %}
     proxy_set_header Host $http_host;
 
     proxy_redirect off;