edje: fix edje RTL description in case of custom state of a part

edje: fix edje RTL description in case of custom state of a part

Summary:
In case of RTL, the "custom" state properties does not apply. It happened because we don't copy the latest src to
dst in set_state(PART:.., "custom", 0.0); in case of dst is already populated.
We should copy the updated src to dst whenever we set the new custom description.

@fix

Reviewers: cedric, raster, jpeg, zmike, jaehwan

Subscribers: kimcinoo, seoz, jpeg

Differential Revision: https://phab.enlightenment.org/D3394