Hide notifications until the device is provisioned.

During Setup (0 == Settings.Secure.DEVICE_PROVISIONED)
there's no reason to show notifications, unless they're
coming from the platform (and therefore essential to the
setup process), like the IME switcher.

We also disable the settings button and ticker while the
device is not provisioned.

Bug: 6355011
Change-Id: I1522f0c0fed3f2f95a36bd71d051248e12f0a1f8