Reduce stestr concurrency to 1 for tempest jobs

The switch from testr to stestr introduced in Change-Id
Icf1f9eb4539666dffb6c9c1651670541523a9f9e missed setting concurrency
jobs to 1 for api and scenario tests, leading to intermittent gate
issues.

This patch also fixes coverage test that got broken in the
aforementioned Change-Id.

Change-Id: I052a9c3b376624f8e9e63faa98f4d09a93bdde4d

neutron_lbaas/tests/tempest/v2/api/test_listeners_admin.py

@@ -93,11 +93,6 @@ class ListenersTestJSON(base.BaseAdminTestCase):
         a missing tenant_id creates the listener with admin
         tenant_id.
         """
-        # TODO(rm_work): Figure out why this test breaks intermittently with
-        # the namespace driver, sometimes on either of py27 or py35
-        self.skipTest(
-            "This is breaking intermittently, and should be fixed, but will "
-            "be skipped until other gate issues are resolved.")
         create_new_listener_kwargs = self.create_listener_kwargs
         create_new_listener_kwargs['protocol_port'] = 8081
         admin_listener = self._create_listener(

neutron_lbaas/tests/tempest/v2/scenario/base.py

@@ -588,7 +588,6 @@ class BaseTestCase(manager.NetworkScenarioTest):
         Check that the requests are not sent to any servers
         Assert that no traffic is sent to any servers
         """
-        time.sleep(10)  # Allow some time for the namespace service to restart
         counters = self._send_requests(self.vip_ip, ["server1", "server2"])
         for member, counter in counters.items():
             self.assertEqual(counter, 0, 'Member %s is balanced' % member)

tox.ini

@@ -30,8 +30,12 @@ commands =
 whitelist_externals = sh
 
 [testenv:cover]
+setenv =
+  {[testenv]setenv}
+  PYTHON=coverage run --source neutron_lbaas --parallel-mode
 commands =
   stestr run {posargs}
+  coverage combine
   coverage report
 
 [testenv:venv]
@@ -89,7 +93,9 @@ commands =
 passenv = TEMPEST_CONFIG_DIR
 setenv =
  OS_TEST_PATH={toxinidir}/neutron_lbaas/tests/tempest/v2/api
- OS_TESTR_CONCURRENCY=1
+commands =
+  stestr run --concurrency 1 {posargs}
+  stestr slowest
 
 # If you are running the tests locally you should set the env variable
 # TEMPEST_CONFIG_DIR=/opt/stack/tempest/etc
@@ -97,7 +103,9 @@ setenv =
 passenv = TEMPEST_CONFIG_DIR
 setenv =
  OS_TEST_PATH={toxinidir}/neutron_lbaas/tests/tempest/v2/scenario
- OS_TESTR_CONCURRENCY=1
+commands =
+  stestr run --concurrency 1 {posargs}
+  stestr slowest
 
 # If you are running the tests locally you should set the env variable
 # TEMPEST_CONFIG_DIR=/opt/stack/tempest/etc
@@ -105,7 +113,9 @@ setenv =
 passenv = TEMPEST_CONFIG_DIR
 setenv =
  OS_TEST_PATH={toxinidir}/neutron_lbaas/tests/tempest/v2/ddt
- OS_TESTR_CONCURRENCY=1
+commands =
+  stestr run --concurrency 1 {posargs}
+  stestr slowest
 
 [testenv:genconfig]
 commands = {toxinidir}/tools/generate_config_file_samples.sh