edje: Fix a major issue with recalc loop

edje: Fix a major issue with recalc loop

With the new Efl.Ui.Clock widget, which implements Datetime,
most parts are relative to each other, and trigger a near-inifinite
recalc of all the parts. Indeed edje was recalculating a part even
if it had already calculated it (flag is set).

This seemingly simple patch fixes Datetime and probably a lot
of other edje widgets.

Fixes T4909

@fix