Switch to using stestr

According to Openstack summit session [1] stestr is maintained project
to which all Openstack projects should migrate.
Let's switch it then.

[1] https://etherpad.openstack.org/p/YVR-python-pti

Change-Id: Ibb1e23aceeb9a864306c52b410bda77736454ef0
Signed-off-by: Chuck Short <chucks@redhat.com>

test-requirements.txt

@@ -7,7 +7,7 @@ eventlet!=0.18.3,!=0.20.1,>=0.18.2 # MIT
 flake8-import-order>=0.13 # LGPLv3
 hacking>=1.0.0,<1.1.0 # Apache-2.0
 mock>=2.0.0 # BSD
-os-testr>=1.0.0 # Apache-2.0
+stestr>=1.0.0 # Apache-2.0
 oslotest>=3.2.0 # Apache-2.0
 testscenarios>=0.4 # Apache-2.0/BSD
 testtools>=2.2.0 # MIT

tox.ini

@@ -14,7 +14,7 @@ deps =
   -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt}
   -r{toxinidir}/test-requirements.txt
   -r{toxinidir}/requirements.txt
-commands = ostestr {posargs}
+commands = stestr run {posargs}
 
 [flake8]
 show-source = True
@@ -43,7 +43,7 @@ setenv = VIRTUALENV={envdir}
          PYTHON=coverage run --source ironic_lib --omit='*tests*' --parallel-mode
 commands =
   coverage erase
-  ostestr {posargs}
+  stestr run {posargs}
   coverage combine
   coverage report --omit='*tests*'
   coverage html -d ./cover --omit='*tests*'