Initial refactor of test_indefinite_freeze_attack.py
Minor edits to comments.
Merge branch 'develop' of https://github.com/theupdateframework/tuf into refactor_test_indefinite_freeze_attack
Re-add repository data for the tests.
Merge pull request #194 from vladimir-v-diaz/refactor_test_indefinite_freeze_attack

Refactor test indefinite freeze attack