Change fsmRename() to take "normal" arguments

Change fsmRename() to take "normal" arguments

- This doesn't need access to the entire fsm, just regular rename()
  args and a flags to see whether "secure" delete should be done.
  In itself this only looks like more trouble, but all the callers
  are fiddling and saving and restoring with fsm->[o]path just
  to call this, which we can now avoid. Leaving sanitizing the
  callers till later though, this is a minefield...