Added tests for host-collection content-host

please review it
thanks
You can make the docstring more complete by adding the command help output:

```python
Usage::

    hammer host-collection content-hosts [OPTIONS]

Options::

    --id ID                       Id of the host collection
    --name NAME                   Host collection name to search by
    --organization ORGANIZATION_NAME Organization name to search by
    --organization-id ORGANIZATION_ID
    --organization-label ORGANIZATION_LABEL Organization label to search by
```