Use openstack-tox-functional
Use openstack-tox-functional

Instead of self-defining a job named tox-functional - and violating the
naming conventions this way - let's use the elsewhere defined common job
openstack-tox-functional.

Change-Id: I6ce2d511f0b3034989d16d8530667c134a3bf900

openstack/rally,openstack/rally,openstack/rally,openstack/rally