Send “rendered” the first time we receive “setHeight”, because then sure...

...ly the gadget has some height to set it to.

Addresses TODO in Versal/player: https://github.com/Versal/player/blob/a8d13f0f7b9b38717eff8a1b0e1de72a50e20113/app/scripts/views/gadget/instance.coffee#L354