TabletStatusBar: Hide notifications during Setup Wizard

Protect tablet users going through the initial setup wizard from trapping
themselves in Settings before the setup wizard is complete. A similar change
was already made for phones, so use the same logic.

Also hide quick-settings button (another way to get trapped in Settings) and
associated panel click handler.  Remove clear button since we're no longer
showing notification items.

Bug: 6704080
Change-Id: If7148cde9d18f493627f8367fd4b39d22e0d5ef1