[webui] Show a login link in kerberos mode

In case that a user logged himself out, he can use that link to login
again.

src/api/app/controllers/webui/user_controller.rb

@@ -5,6 +5,7 @@ class Webui::UserController < Webui::WebuiController
   before_action :check_display_user, only: [:show, :edit, :list_my, :delete, :save, :confirm, :admin, :lock]
   before_action :require_login, only: [:edit, :save, :notifications, :update_notifications, :index]
   before_action :require_admin, only: [:edit, :delete, :lock, :confirm, :admin, :index]
+  before_action :kerberos_auth, only: [:login]
 
   skip_before_action :check_anonymous, only: [:do_login]
 

src/api/app/views/layouts/webui/_personal_navigation.html.erb

@@ -19,6 +19,8 @@
         <%= link_to "Create Home", new_project_path(name: User.current.home_project_name) %>
       <% end %> |
     <%= link_to 'Logout', user_logout_path, method: :post, id: 'logout-link' %>
+  <% elsif CONFIG['kerberos_mode'] %>
+    <%= link_to 'Log In', user_login_path %>
   <% else %>
     <% if CONFIG['proxy_auth_mode'] == :on %>
       <% unless CONFIG['proxy_auth_register_page'].blank? %>