Switch to using stestr

When the TC merged I2637dd714cbb6d38ef8b8dc1083e359207118284 we're
supposed to invoke stestr rather than testr so lets do that

Change-Id: I1b401c583d5e7677fc719bfc4eb2f2bba7b98cfa

tox.ini

@@ -15,7 +15,7 @@ deps =
        -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt}
        -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
-commands = python setup.py testr --testr-args='{posargs}'
+commands = stestr run --slowest {posargs}
 
 [testenv:pep8]
 commands = flake8
@@ -36,7 +36,7 @@ whitelist_externals =
     bash
 commands =
     bash tools/fix_ca_bundle.sh
-    python setup.py testr --testr-args='{posargs}'
+    stestr run --slowest {posargs}
 
 [testenv:functional-v1]
 # TODO(rosmaita): remove this testenv at the beginning
@@ -48,11 +48,16 @@ whitelist_externals =
     bash
 commands =
     bash tools/fix_ca_bundle.sh
-    python setup.py testr --testr-args='{posargs}'
+    stestr run --slowest {posargs}
 
 [testenv:cover]
-commands = python setup.py testr --coverage --testr-args='{posargs}'
-           coverage report
+setenv =
+    PYTHON=coverage run --source glanceclient --parallel-mode
+commands =
+    stestr run {posargs}
+    coverage combine
+    coverage html -d cover
+    coverage xml -o cover/coverage.xml
 
 [testenv:docs]
 deps = -r{toxinidir}/doc/requirements.txt