PhoneWindowManager: Fix issues introduced with runtime navbar

* With system settings we need to pass UserHandle.USER_CURRENT
  to make sure we are getting proper value, otherwise we always
  end up getting '0'. Also we need to make sure to set valid
  mHasNavigationBar in setInitialDisplaySize().

Change-Id: I3efd614e735f9a602f13263a742ce858a9d14769