Don't show download toast during SUW

Check to see if setup wizard is running before showing toast to
inform user that a download was started. Note that this will only
affect the device owner; when adding new users later, the toast
will still appear. (The USER_SETUP_COMPLETE flag is hidden from
the SDK, while DEVICE_PROVISIONED remains available.)

Bug: 22594336
Change-Id: I57c42d6f821714b71cbb066e82bba2a1dbab4951