Allow passing dictionaries to KazooClient.__init__() for connection_retry and command_retry

Per the code documentation:

```
:param connection_retry:
    A :class:`kazoo.retry.KazooRetry` object to use for
    retrying the connection to Zookeeper. Also can be a dict of
    options which will be used for creating one.
:param command_retry:
    A :class:`kazoo.retry.KazooRetry` object to use for
    the :meth:`KazooClient.retry` method. Also can be a dict of
    options which will be used for creating one.
```

The useful feature of passing in a `dict` in place of a `KazooRetry` was not working correctly due to the way that `KazooClient.__init__()` was handling the `connection_retry` and `command_retry` kwargs. This patch fixes the issue and keeps the code documentation honest.