Added test for removehostcollection for activationkey

Please review it
thanks
@tkolhar, there is no need for you to take action here, but just take the time to read through my comments.

I know I harp on the subject of formatting a lot, but it really does make a difference. Nicely formatted code lets me concentrate on _what_ you're saying, not _how_ you're saying it. Something like this would be better:

```python
@classmethod
def remove_host_collection(cls, options=None):
    """Remove the associated resource."""  # this docstring is useless
    cls.command_sub = 'remove-host-collection'
    return cls.execute(cls._construct_command(options))
```

That said, I've looked through the module that this class method is in, and every single command has similar formatting.

Also, the docstring in that module is broken. Try issuing `make docs-clean; make docs` sometime and reading through the warnings. If you have trouble understanding the warnings, the [reStructuredText Markup Specification](http://docutils.sourceforge.net/docs/ref/rst/restructuredtext.html) is a good, definitive resource.