Description of problem:
Deleting a disk of RHV VM via API throws an error `Error: HTTP response code is 405. The response body is empty.` in the response.

Version-Release number of selected component (if applicable):
5.10.0.31

How reproducible:
Always

Steps to Reproduce:
1. Create an RHV VM.
2. Add a disk to the VM.
3. Send an API request to delete the disk from VM.
POST /api/requests
Query: {
    "action"  :"create",
    "options" : {
                  "src_ids" : [
                                ":vm_id"
                               ],
                  "request_type" : "vm_reconfigure",
                  "disk_remove" : [
                                    {   
                                     "disk_name"      : ":disk_id",
                                     "delete_backing" : false
                                    }
                                   ]
                 },
    "auto_approve" : false
}
Actual results:
Request results in error - `Error: HTTP response code is 405. The response body is empty.`
Disk is not deleted from the VM.

Expected results:
The request must be completed successfully, and disk must be deleted from the VM.

Additional info:
No matter what the VM power state is, the request always results in the same error.