Minor fixes to Launcher

Minor fixes to Launcher

- Adding checks to prevent multiple onSetAlpha's to be called (especially now that we are using display lists)
- Removing an old change to keep artificially make the last page wider
- Fixing issue where you could click on an item in the paged view while the page it was on is being faded out

Change-Id: I9b194565602b5200c0688da2caec9c3c829b3bb0