Allow duplicated container name by default

In before, the default config disallow duplicated name within
tenant. This is a bad default because zun auto-generate container
name if it is not specified. It is possible that the same name
is generated twice which causes failure. This makes our API
unpredictable which is not a good practice. Therefore, we changed
the default to allow duplicated name.

Change-Id: Ic0f4d1279c0822aceac9e1983dc500afe9834a59

zun/conf/compute.py

@@ -25,7 +25,7 @@ service_opts = [
 db_opts = [
     cfg.StrOpt(
         'unique_container_name_scope',
-        default='project',
+        default='',
         choices=['', 'project', 'global'],
         help="""
 Sets the scope of the check for unique container names.

zun/tests/unit/db/test_container.py

@@ -200,6 +200,8 @@ class DbContainerTestCase(base.DbTestCase):
         self.assertEqual(new_image, res.image)
 
     def test_update_container_with_the_same_name(self):
+        CONF.set_override("unique_container_name_scope", "project",
+                          group="compute")
         container1 = utils.create_test_container(
             name='container-one',
             uuid=uuidutils.generate_uuid(),
@@ -412,6 +414,8 @@ class EtcdDbContainerTestCase(base.DbTestCase):
     @mock.patch.object(etcd_client, 'update')
     def test_update_container_with_the_same_name(self, mock_update,
                                                  mock_write, mock_read):
+        CONF.set_override("unique_container_name_scope", "project",
+                          group="compute")
         mock_read.side_effect = etcd.EtcdKeyNotFound
         container1 = utils.create_test_container(
             name='container-one',