New os-testr uses stestr under the hood, which creates .stestr but not
.testrepository directory in the current dir. Other than that, it
doesn't seem like there is any difference in the format or names of
files generated in the directory.
Change-Id: Iead2b550fc2c3accf25e450db0eb0a56603fc571
Closes-Bug: #1716746
Kien Nguyen