framework: Close system windows when performing 'switch to last app' action

This fixes a bug where performing the action while on the recent apps screen
would cause the next attempt to open recent apps require two presses of the
recent apps button (the first press would toggle it closed, rather than open).

It also prevents the switch from being obscured by the notifications shade.

Change-Id: I2220149ce604a25501121abc29e5d88f8b1cbf4f