Use PBR's setup.py test command

There is setup.py test provided by pbr and there is setup.py testr
provided by testr. The `test` command is still supported by PBR and is a
semi standard way of doing things whereas `testr` in upstream testr is
not really supported by them. Therefore use `test`.

Change-Id: I77f37fd2287204e8f1e7f5a96f47453eb10e720d

tox.ini

@@ -15,7 +15,7 @@ install_command = pip install {opts} {packages}
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
 commands =
-  python setup.py testr --slowest --testr-args='{posargs}'
+  python setup.py test --slowest --testr-args='{posargs}'
 
 [testenv:bindep]
 # Do not install any requirements. We want this to be fast and work even if
@@ -32,7 +32,7 @@ commands = flake8 {posargs}
 
 [testenv:cover]
 commands =
-  python setup.py testr --coverage
+  python setup.py test --coverage
 
 [testenv:docs]
 commands = python setup.py build_sphinx
@@ -46,7 +46,7 @@ commands = zuul-server -c etc/zuul.conf-sample -t -l {posargs}
 [testenv:nodepool]
 setenv =
    OS_TEST_PATH = ./tests/nodepool
-commands = python setup.py testr --slowest --testr-args='--concurrency=1 {posargs}'
+commands = python setup.py test --slowest --testr-args='--concurrency=1 {posargs}'
 
 [flake8]
 # These are ignored intentionally in openstack-infra projects;