Eliminate unnecessary fsm->path/opath shuffle on backup renaming

Eliminate unnecessary fsm->path/opath shuffle on backup renaming

- Makes the code much more obvious to follow since we're not swapping
  path/opath back and forwards just to be able to use a throwaway
  path for the rename. Dont bother null-checking on logging,
  if one of the paths was null we'd be dead already.
- Also fixes an ancient memleak: when osuffix is in use, fsm->path
  gets newly malloced before fsmVerify() but this part did another
  allocation on it, didn't save and restore fsm->path .. and nothing
  was freeing the original (local) allocation of fsm->path, only
  restoring the previous value.