bugfix [zwave][climate]current temp could be none at init

[turbokongen]

Description:

Fixes the following issue in dev branch:

Related issue (if applicable): fixes #

�[31m17-03-23 18:12:14 ERROR (Dummy-14) [openzwave] Error in manager callback�[0m
Traceback (most recent call last):
  File "/srv/hass/lib/python3.4/site-packages/openzwave-0.3.2-py3.4.egg/openzwave/network.py", line 948, in zwcallback
    self._handle_value_added(args)
  File "/srv/hass/lib/python3.4/site-packages/openzwave-0.3.2-py3.4.egg/openzwave/network.py", line 1478, in _handle_value_added
    'value' : self.nodes[args['nodeId']].values[args['valueId']['id']]})
  File "/srv/hass/lib/python3.4/site-packages/PyDispatcher-2.0.5-py3.4.egg/pydispatch/dispatcher.py", line 338, in send
    **named
  File "/srv/hass/lib/python3.4/site-packages/PyDispatcher-2.0.5-py3.4.egg/pydispatch/robustapply.py", line 55, in robustApply
    return receiver(*arguments, **named)
  File "/srv/hass/src/home-assistant/homeassistant/components/zwave/__init__.py", line 291, in value_added
    hass, schema, value, config, device_config)
  File "/srv/hass/src/home-assistant/homeassistant/components/zwave/__init__.py", line 641, in __init__
    self.check_value(value)
  File "/srv/hass/src/home-assistant/homeassistant/components/zwave/__init__.py", line 670, in check_value
    self._check_entity_ready()
  File "/srv/hass/src/home-assistant/homeassistant/components/zwave/__init__.py", line 730, in _check_entity_ready
    node_config=node_config, hass=self._hass)
  File "/srv/hass/src/home-assistant/homeassistant/components/climate/zwave.py", line 38, in get_device
    return ZWaveClimate(values, temp_unit)
  File "/srv/hass/src/home-assistant/homeassistant/components/climate/zwave.py", line 71, in __init__
    self.update_properties()
  File "/srv/hass/src/home-assistant/homeassistant/components/climate/zwave.py", line 116, in update_properties
    round((float(self._current_temperature)), 1))
TypeError: float() argument must be a string or a number, not 'NoneType'�[0m

[mention-bot]

@turbokongen, thanks for your PR! By analyzing the history of the files in this pull request, we identified @balloob, @fabaff and @armills to be potential reviewers.