proxyAuth: allow protecting specific subpath

while I don't think this is useful for apps, it is useful for e2e test atleast

src/proxyauth.js

@@ -142,7 +142,7 @@ function authorize(req, res, next) {
 
 function logoutPage(req, res) {
     res.clearCookie('authToken');
-    res.redirect('/login');
+    res.redirect('/'); // do not redirect to '/login' as it may not be protected
 }
 
 function logout(req, res, next) {