Disable quick settings for users until USER_SETUP_COMPLETE.

If the current user has not yet made it through the setup wizard,
disable the quick settings panel entirely.

Use Settings.Secure.USER_SETUP_COMPLETE as the signal.  This is a
per-user setting, so be careful to observe only on the current user's
behalf.

Bug:6712493
Change-Id: I3076a8a550165a9eeccf7fb129d470ef4ddeaed4