Fix weirdness with pressing SHIFT & ALT on the home screen - fixes #1490

Fixes issue where pressing SHIFT while releasing ALT in the favorites/home screen, the activities remain in gray (new instance) mode.

Google code in task:  https://www.google-melange.com/gci/task/view/google/gci2014/5234039246028800

Bug link:  http://bugs.sugarlabs.org/ticket/1490