Added scheme to OutputCacheKey to prevent SSL bypass

Fixes #6850.

src/Orchard.Web/Modules/Orchard.OutputCache/Filters/OutputCacheFilter.cs

@@ -370,6 +370,9 @@ namespace Orchard.OutputCache.Filters {
             foreach (var p in filterContext.ActionParameters)
                 result.Add("PARAM:" + p.Key, p.Value);
 
+            // Vary by scheme.
+            result.Add("scheme", filterContext.RequestContext.HttpContext.Request.Url.Scheme);
+
             // Vary by theme.
             result.Add("theme", _themeManager.GetRequestTheme(filterContext.RequestContext).Id.ToLowerInvariant());