Show global actions instead of assistant for LPP in setup wizard

Assistant can't be opened during device setup, and new users may not
know how to get to the power menu if LPP is assigned to the assistant,
so this ensures they can find a way to turn off or reboot the device.

Bug: 190432896
Test: Ensure LPP is configured to start the assistant. Then,
      adb shell settings put global device_provisioned 0
      and LPP should open global actions, then
      adb shell settings put global device_provisioned 1
      and it should be the assistant again.
Test: Also test using the actual setup wizard flow.
Change-Id: Ida693297a03d0eda08b557078868de77f3902e2d