Switch rally trunk scenario to use new rally validators

Validators like:
* rally.task.validation.required_openstack
* rally.task.validation.required_services
are deprecated in Rally 0.10.0 [1].

Instead of calling it directly they should be used via
new decorator 'rally.common.validation.add' and this commit
switches it to use validators in new way.

[1] https://tinyurl.com/y94sfct2

Change-Id: I2883eb94e2532a10160305b283e2d64b93443909

rally-jobs/plugins/trunk_scenario.py

@@ -11,18 +11,18 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+from rally.common import validation
 from rally import consts
 from rally.plugins.openstack import scenario
 from rally.plugins.openstack.scenarios.neutron import utils
 from rally.task import atomic
-from rally.task import validation
 
 
 """Scenarios for VLAN Aware VMs."""
 
 
-@validation.required_services(consts.Service.NEUTRON)
-@validation.required_openstack(users=True)
+@validation.add("required_services", services=[consts.Service.NEUTRON])
+@validation.add("required_platform", platform="openstack", users=True)
 @scenario.configure(context={"cleanup@openstack": ["neutron"]},
                     name="NeutronTrunks.create_and_list_trunk_subports")
 class TrunkLifeCycle(utils.NeutronScenario):