Remove popup and timer before powering off

Remove popup and timer before powering off

1. Remove popup before powering off
Low and critical popups are shown beforehand according to battery level.
So, to show popup before powering off is duplicated action.

2. Remove poweroff timer
The purpose of power off timer is to have time to show popup before powering off.
But we don't need it any more.
Morever, popup can be shown or not shown by remained battery capacity.
It can confuse users.

Change-Id: I8cc67999cfe7be56e4c882012b4be29800cd4159
Signed-off-by: lokilee73 <changjoo.lee@samsung.com>