Refs #22285 - Correctly calculate object type in host form

Otherwise, discovered hosts add a field named
`discovered_host[puppetclass_ids][]` that fails on smart params which
expects the whole form to be submitted under the `host` hash.

app/views/puppetclasses/_class_selection.html.erb

@@ -9,7 +9,7 @@
   <div class="col-md-4 classes">
     <h3><%= _('Included Classes') %></h3>
 
-    <%= hidden_field_tag "#{type}[puppetclass_ids][]" %>
+    <%= hidden_field_tag "#{obj_type(obj)}[puppetclass_ids][]" %>
 
     <ul id="selected_classes">
       <% if authorized_for(:controller => :host_editing, :action => :edit_classes) %>