Further tweak the config file removal/backup logic to make it clearer

Further tweak the config file removal/backup logic to make it clearer

- Turn the strange negated condition around: when dealing with
  config files test for it directly. This way, all the special
  cases are handled first and normal cases fall through the if-jungle
  to exactly one case of rpmfsSetAction(fs, i, FA_ERASE). Makes
  the logic more obvious, at least to me.