Evalute adding serial decorator to tests

Change-Id: Icb56caf688b20c02822d19484acbed54a9162535

.zuul.yaml

@@ -47,7 +47,6 @@
       - ^test-requirements.txt$
     vars:
       tox_envlist: all
-      tempest_concurrency: 1
       tempest_test_regex: ^whitebox_tempest_plugin\.
       # NOTE(jparker) in order for guest to boot via UEFI, the host will need the
       # open source implementation of UEFI for VMs via the OVMF package. In
@@ -153,7 +152,6 @@
       - ^whitebox_tempest_plugin/api/compute/(?!test_rbd_direct_download).*py$
     vars:
       tox_envlist: all
-      tempest_concurrency: 1
       compute_node_template_name: whitebox-devstack-ceph-multinode.yaml.j2
       devstack_plugins:
         whitebox-tempest-plugin: https://opendev.org/openstack/whitebox-tempest-plugin.git

whitebox_tempest_plugin/api/compute/base.py

@@ -37,6 +37,11 @@ LOG = logging.getLogger(__name__)
 
 class BaseWhiteboxComputeTest(base.BaseV2ComputeAdminTest):
 
+    # Decorator support for serial does not land into tempest until 34.0.0.
+    # Explicitly setting _serial to True instead of using the decorator to
+    # avoid clashing with downstream execution.
+    _serial = True
+
     def create_test_server(self, *args, **kwargs):
         """Whitebox is able to completely fill its compute hosts because it
         runs with things like PCI devices and dedicated CPUs. Because of that