Description of problem:
Cannot list/update/remove puppetclasses via API calls.


Version-Release number of selected component (if applicable):
Satellite 6.3.3

How reproducible:
100%

Steps to Reproduce:
satellite-6.3.3-2.el7sat.noarch
~~~
List puppet class ids for host 38:
~~~
# curl --user admin:pass -X GET https://$(hostname -f)/api/v2/hosts/38/puppetclass_ids 
{"results":[]}
~~~

A puppet class is present as can be seen:
# hammer host puppet-classes --host-id 38
~~~
---|-----------------------
ID | NAME                  
---|-----------------------
1  | access_insights_client
---|-----------------------

Try in a different way to list puppet classes for host 38:
# curl --user admin:pass -X GET https://$(hostname -f)/api/v2/hosts/38/puppetclasses
~~~
{
  "total": 1,
  "subtotal": 1,
  "page": 1,
  "per_page": 20,
  "search": null,
  "sort": {
    "by": null,
    "order": null
  },
  "results": {"access_insights_client":[{"id":1,"name":"access_insights_client","created_at":"2018-02-08T09:45:40.550Z","updated_at":"2018-02-08T09:45:40.550Z"}]}
}
~~~

Try to delete a puppetclass for host 38
# curl --user admin:pass -X DELETE https://$(hostname -f)/api/v2/hosts/38/puppetclass_ids/1
~~~
[]
~~~

Conclusion: It did not delete the puppetclass from host 38


Same tests on satellite-6.4.0-15
~~~
List puppet class ids for host 528:
# curl --user admin:pass -X GET https://$(hostname -f)/api/v2/hosts/528/puppetclass_ids
{"results":[16,78]}

Remove puppet class id 16 from host 528:
# curl --user admin:pass -X DELETE https://$(hostname -f)/api/v2/hosts/528/puppetclass_ids/16
[]

List class ids for host 528:
# curl --user admin:pass -X GET https://$(hostname -f)/api/v2/hosts/528/puppetclass_ids
{"results":[78]}
~~~

Actual results:
API calls on Satellite 6.3.3 yield no results

Expected results:
API calls on Satellite 6.3.3 to do the same as in Satellite 6.4

Additional info:
As a workaround we created a new hostgroup that does not contain the puppetclass you want to remove and assigned it to the host. This inherits the puppet classes.