Merge pull request #1719 from hakanensari/mounted-app-redirect

Fix redirect when authenticating mounted apps

lib/devise/failure_app.rb

@@ -88,6 +88,7 @@ module Devise
       opts  = {}
       route = :"new_#{scope}_session_path"
       opts[:format] = request_format unless skip_format?
+      opts[:script_name] = nil
 
       context = send(Devise.available_router_name)