Description of problem:

During provisioning hosts, new hosts does not provide options to exclude puppet classes coming from parent or nested hostgroups.

Customer wants to remove puppet classes which are already included and listed in
"Included Classes" section. This listed classes are coming/inherited from the selected hostgroup in 'Host Group' dropdown under Host tab. These hostgroup can be either parent or nested.

How reproducible:
Steps to Reproduce:
1. Create new host group (Configure>Host Groups> New Host Group)
2. Under Host Group tab, select appropriate CV and Puppet Environment.
3. Select Puppet Class tab, and add some modules and submit. Here, I selected four classes. You can create nested hostgroup as well and add more puppet classes.

4. Hosts>New Hosts> Select Host Group (Parent host group or Nested Host).
5. Under Puppet Class tab, all the puppet classes listed in "Included Classes". These inherited classes be excluded and are grey-out. 

Actual results:
We can add new classes during new host provisioning. But we do not have option to exclude puppet classes which are coming from hostgroup.

Expected results:
Customer want to exclude the puppet classes that's been inherited into a new host through selected hostgroup. 

Additional info:
Looking on Foreman projects there appears to be an existing RFE: http://projects.theforeman.org/issues/6416
linked to bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1294074

However, the bugzilla is more around excluding inherited modules from nested hostgroups whereas our focus is on excluding them directly on hosts. Even we select parent hostgroup or nested hostgroup, we should be able to exclude the puppet classes from the hosts listed in "Included Classes".