rally: switch to new format for context name

Since I9d3bafa075631a3f48cbd3627a4cc1a5a859cce2 in rally, platform
should be part of context name (context@platform).

Otherwise, a warning message (or even breakage because of
I10ac687f9f420dcf0d907b51d5d9303f68d35719) may be triggered.

Change-Id: I6f84282d22d13d36dcba221ab9d94c3fda95f130

rally-jobs/plugins/trunk_scenario.py

@@ -23,7 +23,7 @@ from rally.task import validation
 
 @validation.required_services(consts.Service.NEUTRON)
 @validation.required_openstack(users=True)
-@scenario.configure(context={"cleanup": ["neutron"]},
+@scenario.configure(context={"cleanup@openstack": ["neutron"]},
                     name="NeutronTrunks.create_and_list_trunk_subports")
 class TrunkLifeCycle(utils.NeutronScenario):