Fixing Heads Up Notifications not reacting to action touches in split shade

HUN was not reacting to touches because notification was shifted too low and touch-enabled region was not moving with it. The fix is to not shift notification that much in split shade mode - extra shift was introduced by split shade status bar. Now split shade status bar margin is accounted for in HUN shift calculation.
Also some small cleaning of dead code which I was trying to read :)

Fixes: 201262024
Test: StackScrollAlgorithmTest
Change-Id: I50498c3e038651ff9ee38e9741056933f0c369c8