Added tests for host-collection content-host

please review it
thanks
Make sure to indent code blocks. and separate paragraphs of text. For example:

```python
    @classmethod
    def content_hosts(cls, options=None):
        """
        List content-hosts added to the host collection

        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
        """
        cls.command_sub = "content-hosts"
        return cls.execute(cls._construct_command(options), expect_csv=True)
```