init: fix run level switching, tidy up stuff we don't need to do

init: fix run level switching, tidy up stuff we don't need to do

There's no pint trying to create a new utmp - the root fs will be r/o at
that point

The extra fd manipulation is guaranteed not required

No point doing work to change from run level to the same one !

The main change however is to set the runlevel before we task switch