Description of problem:
Module ovirt_host_facts returns more on <cluster> than needed when not nested.

Version-Release number of selected component (if applicable):
ansible-2.8.0-0.9.rc3.el7ae.noarch

How reproducible:always


Steps to Reproduce:
1. run playbook like:
      ovirt_host_facts:
        auth: "{{ ovirt_auth }}"
        pattern: "name=vhost*"
        fetch_nested: True
        nested_attributes:
          - name

returns correctly:

            "cluster": {
                "href": "/ovirt-engine/api/clusters/87c0c65c-f3b1-11e8-9209-001a4a013f36",
                "id": "87c0c65c-f3b1-11e8-9209-001a4a013f36",
                "name": "Default"
            },

2. run the same playbook with fetch_nested: False


Actual results: cluster with all information
          "cluster": {
                "affinity_groups": [],
                "ballooning_enabled": false,
                "comment": "",
                "cpu": {
                    "architecture": "x86_64",
                    "type": "Intel Westmere Family"
                },
....


Expected results:
            "cluster": {
                "href": "/ovirt-engine/api/clusters/87c0c65c-f3b1-11e8-9209-001a4a013f36",
                "id": "87c0c65c-f3b1-11e8-9209-001a4a013f36",
            },


Additional info:
In module ovirt_vm_facts it works as expected.