Trigger controller override calculation when zone current temperature changes

[lievendf]

Tested by warming up the temperature sensor, verified override changes in debug logging.
Not 100% sure about the isinstance check copied from if statement above, but it seems to work...

[nielsfaber]

Thanks for your PR.

I think we should discuss a little bit more how this improvement should work.
As mentioned in your question thread I have some concerns which don't seem to be considered in your implementation:

However, it should be prevented that in every step of temperature change this updating occurs.
Most TRVs have 0.1C resolution, so recalculating on every step would cause a lot of commands being sent to the thermostat.
In addition, this integration can support multiple zones, so any temperature change in any zone could trigger recalculation.