menu: modified move function

menu: modified move function

Let's keep the emulator window covered with transparent widget
while moving, to handle mouse events conveniently. However,
display region is excepted. Display can be drawn black or frozen
screen if it has a transparent layer on it. So, to avoid this issue,
display handles mouse events directly while moving, instead of
helping of transparent widget.

Change-Id: I37d69f1c041843fdaa61244268d06bbf0af7c20b
Signed-off-by: GiWoong Kim <giwoong.kim@samsung.com>