elm_panel: set scrollable panel unfocusable when closed

elm_panel: set scrollable panel unfocusable when closed

 - When scrollable panel is closed by elm_panel_hidden_set(),
   elm_panel_toggle() APIs, it shows animation with scroller bringin
   effect.
 - During this animation, panel is still focusable, and may stop closing
   when content gets focused.
 - scrollable panel is now set unfocusable when closed by APIs above, and
   set focusable when opened after bringin animation.

origin: upstream(f4d5d57e17496098eeb9427a5b196d26963d5c78)

Change-Id: I43e32a10845f81a3c146a2dbd59093b6606c6759
Signed-off-by: Sungtaek Hong <sth253.hong@samsung.com>