Description of problem:
API should not be declaring HTTP DELETE verb on collections. In this specific case, API was allowing DELETE on the pxe_servers collection which causes incorrect representation of actions when fetching pxe_servers.

Version-Release number of selected component (if applicable):
5.11.0.13

How reproducible:
Always

Steps to Reproduce:
1. Get an appliance
2. Fetch pxe_servers via GET /api/pxe_servers

Actual results:
You will notice the following 2 entries in the collection actions:
 {'name': 'edit',
  'method': 'patch',
  'href': 'https://<ip_address>/api/pxe_servers'},
 {'name': 'delete',
  'method': 'delete',
  'href': 'https://10.8.199.37/api/pxe_servers'}

Expected results:
Only the "post" method should be exposed, 'patch' and 'delete' must not be present.

Additional info:
Reference BZ -https://bugzilla.redhat.com/show_bug.cgi?id=1392595