Since https://review.openstack.org/#/c/281779/2 have been
merged the telemetry integration job is broken.
Unfortunatly, it can't be fixed on our side, because we have to
rename SERVICE_TENANT_NAME in many devstack plugin, we can't merge thing
until all plugins have been fixed.
So this change restores SERVICE_TENANT_NAME, to be able to switch to SERVICE_PROJECT_NAME.
Related-bug: #1548634
Change-Id: I14ebf23aa63f0f153b934ad213a6209d22e73e9d