* Rename _update() to update()
A platform neeed a function update(), even though
polling is false, this is due to the service:
homeassistant.update_entity, which calls update()
* Update test harnesss to script testing.
Test homeassistant.update_entity in all platforms.
This call calls update() in the platform to get
a new reading.
* Add reuse parameter.
* Move service call from helper to tests.
* Change run_service_update --> prepare_service_update.
* Remove entity_id parameter.
8adbc62a6e