Added test for add-contenthost/removecontenthost for host-collection

please review it
thanks
Better to read:

```python
new_system = make_content_host({
    u'name': content_host_name,
    u'organization-id': self.org['id'],
    u'content-view-id':
    self.DEFAULT_CV['id'],
    u'lifecycle-environment-id':
    self.LIBRARY['id']
})
```