Correctly pass kwargs through to wheel.call_func

The change in 1de6204 broke what ``format_call()`` expects in [wheel.Wheel().call_func()](https://github.com/whiteinge/salt/blob/36f70bdcecb7ad89dc6e939d8743f8db3eb4b48b/salt/wheel/__init__.py#L56). That said I'm not sure what nested kwargs are or where they're used so this commit may very well break something elsewhere. In my simple tests ``clear_load`` never contained a ``kwarg`` value so I'm submitting this change for review.

@thatch45 ping