Fix current_temperature is rounded

[aufano]

Description:

Fix now when temperature_unit == unit_of_measurement the convert_to_display will round it.

Related issue (if applicable): fixes #

Pull request in home-assistant.github.io with documentation (if applicable): home-assistant/home-assistant.github.io#<home-assistant.github.io PR number goes here>

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• Documentation added/updated in home-assistant.github.io

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[emlove]

See also #4522

[aufano]

I dont know the right way to fix the problem because in the #4522 @balloob said "Do not convert when passed in unit is already expected unit" but the problem is that my zwave radiator pass a lot of decimals in celsius and I have my home assistant temperature in celsius too.., so the code don't round it.

[emlove]

I think this is a reasonable fix myself, but I want to make sure we're looking at the whole history of this code in case there was some other relevant side-effect from the previous PR. (Want to make sure we're jogging @balloob's memory. 😄 )

In any case showing all of the decimal places in the frontend is a defect IMO, and we need some solution.

[balloob]

Yeah this looks good. Thanks for the fix 🐬

[balloob]

Cherry-picked into the 0.42 branch