Temporarily hide lock screen unlock targets if opening a widget

If the user selects a widget to open, it's very unlikely that they would
want to use any of the slider shortcuts at that moment. Make it easier
to unlock the screen and open the desired widget by temporarily hiding
other targets.

Change-Id: I51d879cc77826e4f7235c5d35b6352e5e83bb7cf
Framework: Fixes in Lock screen notifications

Change-Id: Ie77733598c6cb76e43f1d53c05ed503c6bb322c7