Engine: test/model: enable & fix several model tests

Enable & fix the following model tests:
- deletion changeset
- erratum rule
- filter
- package group rule
- package rule
Merge pull request #3398 from bbuckingham/engine-model_tests

Engine: test/model: enable & fix several model tests
Engine: Refs #3585 - Fix user model test
Merge pull request #3407 from daviddavis/temp/20131119142527

Engine: Refs #3585 - Fix user model test