Fix launcher invisibility bug

There was a bug in the DisplayList code for layers where we would
set the alpha value for a layer only if the alpha were non-1. This works
most of the time (since the value is usually 1 and doesn't need to
be set at all, and if the value is non-1, it is set correctly). But when
the value has been set to a non-1 value, setting alpha back to 1 cannot happen
due to this logic. This caused launcher to have some invisible pages when
returning to Home because those pages previously had an alpha value of 0, and
setting the alpha to 1 had no effect due to this DisplayList code.

The fix is to simply remove the check for non-1 values; we should
always set the alpha value of layers to handle all cases.

Issue #6413892 alpha value is messed up after AlphaAnimation

Change-Id: Ia51acb2eaaf0609ea7189998ed449bdd9ea7e05f