Merge branch 'demo2' of https://github.com/theupdateframework/tuf into demo2
Merge branch 'demo2' of https://github.com/theupdateframework/tuf into demo2
Merge branch 'demo2' of https://github.com/theupdateframework/tuf into demo2
Update test_util_test_tools.py following change to util_test_tools.init_repo()

A util_test_tools.init_repo() parameter name was changed from 'tuf' to 'using_tuf', however, test_util_test_tools was not updated following the name change.