Add method to reset PublishedContentRequest template

src/Umbraco.Web/Routing/PublishedContentRequest.cs

@@ -312,6 +312,16 @@ namespace Umbraco.Web.Routing
             TemplateModel = template;
         }
 
+        /// <summary>
+        /// Resets the template.
+        /// </summary>
+        /// <remarks>The <c>RenderingEngine</c> becomes unknown.</remarks>
+	    public void ResetTemplate()
+	    {
+	        EnsureWriteable();
+	        TemplateModel = null;
+	    }
+
         /// <summary>
         /// Gets a value indicating whether the content request has a template.
         /// </summary>