fix LDAP omniauth regression (Closes: #22357)

~~~~
ActionView::Template::Error (undefined method `user_omniauth_callback_path'
~~~~
Signed-off-by: Dmitry Smirnov <onlyjob@member.fsf.org>

app/views/devise/sessions/_new_ldap.html.haml

-= form_tag(user_omniauth_callback_path(server['provider_name']), id: 'new_ldap_user' ) do
+= form_tag(omniauth_callback_path(:user, server['provider_name']), id: 'new_ldap_user') do
   = text_field_tag :username, nil, {class: "form-control top", placeholder: "#{server['label']} Login", autofocus: "autofocus"}
   = password_field_tag :password, nil, {class: "form-control bottom", placeholder: "Password"}
   - if devise_mapping.rememberable?