fix: mounting of all-route middlewares to router instead of app

related to julianlam/nodebb-plugin-session-sharing#73
These three lines haven't changed in two years, but it makes more
sense for them to be called against the relative path router,
otherwise req.originalUrl contains the relative path, which is
not necessary.

src/routes/index.js

@@ -95,12 +95,11 @@ module.exports = function (app, middleware, callback) {
 	router.render = function () {
 		app.render.apply(app, arguments);
 	};
-	var relativePath = nconf.get('relative_path');
 	var ensureLoggedIn = require('connect-ensure-login');
 
-	app.all(relativePath + '(/+api|/+api/*?)', middleware.prepareAPI);
-	app.all(relativePath + '(/+api/admin|/+api/admin/*?)', middleware.isAdmin);
-	app.all(relativePath + '(/+admin|/+admin/*?)', ensureLoggedIn.ensureLoggedIn(nconf.get('relative_path') + '/login?local=1'), middleware.applyCSRF, middleware.isAdmin);
+	router.all('(/+api|/+api/*?)', middleware.prepareAPI);
+	router.all('(/+api/admin|/+api/admin/*?)', middleware.isAdmin);
+	router.all('(/+admin|/+admin/*?)', ensureLoggedIn.ensureLoggedIn(nconf.get('relative_path') + '/login?local=1'), middleware.applyCSRF, middleware.isAdmin);
 
 	app.use(middleware.stripLeadingSlashes);