Add missing tab for Kerberos

Signed-off-by: Rémy Coutable <remy@rymai.me>

app/views/devise/shared/_tabs_ldap.html.haml

 %ul.new-session-tabs.nav-links.nav-tabs
   - if crowd_enabled?
     %li.active
-      = link_to "Crowd", "#tab-crowd", 'data-toggle' => 'tab'
+      = link_to "Crowd", "#crowd", 'data-toggle' => 'tab'
+  - if kerberos_enabled?
+    %li{class: (:active unless crowd_enabled? || ldap_enabled?)}
+      = link_to "Kerberos", "#kerberos", 'data-toggle' => 'tab'
   - @ldap_servers.each_with_index do |server, i|
     %li{class: (:active if i.zero? && !crowd_enabled?)}
-      = link_to server['label'], "#tab-#{server['provider_name']}", 'data-toggle' => 'tab'
+      = link_to server['label'], "##{server['provider_name']}", 'data-toggle' => 'tab'
   - if signin_enabled?
     %li
-      = link_to 'Standard', '#tab-signin', 'data-toggle' => 'tab'
+      = link_to 'Standard', '#ldap-standard', 'data-toggle' => 'tab'