Ehm, %pretrans failure shouldn't abort the entire transaction

Ehm, %pretrans failure shouldn't abort the entire transaction

- Brainfart in previous commit (71c6b06b3f240021f2ece46f9cf7aa891f716710):
  %pretrans failure should only cause that package to fail, not
  abort the entire transaction. Doh.
- Failures are tracked via transaction elements but pre/posttrans
  were specifically filtered out. All we need is removing that filtering
  and the warn-only vs error logic in psm takes care of the rest.
  The transaction.c changes in previous commit were just unnecessary.