This commit removes .testr.conf since this repo already has
.stestr.conf. We just need .stestr.conf instead of .testr.conf.
Change-Id: Ib084dbbb4c06f57e1eb15748e992e09444cec63b
Add unit tests for persister.py in root directory.
Additionally:
* switched to testr as it seems to be used in many
openstack projects
* enabled coverage
Change-Id: I429ef6a900808c192ad5613c13808583d33fde24