genlist: scroll to item when calc is done

genlist: scroll to item when calc is done

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   genlist: scroll to item when calc is done

   Summary:
   If elm_genlist_item_bring_in() is called immediately after appending
   item, genlist will not scroll to the last one but stop in the middle.
   This patch blocks genlist from scrolling to not calculated item.

   Reviewers: cedric, SanghyeonLee

   Reviewed By: SanghyeonLee

   Subscribers: jpeg

   Differential Revision: https://phab.enlightenment.org/D3861
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Change-Id: I4e9af177bce95fabe687bb41b470743a4b8abb1d
Signed-Off-By: Jee-Yong Um <jc9.um@samsung.com>