Fix grenade job selection for newton
Fix grenade job selection for newton

We want to run mitaka to newton upgrades on trusty because mitaka starts
first and was never tested with xenial. Fix this in zuul layout.

Basically we currently have:

  EOL -> liberty (no test)
  liberty -> mitaka (trusty)
  mitaka -> newton (trusty)
  mitaka -> master (trusty)

Then as soon as newton is properly branched everywhere we want:

  EOL -> liberty (no test)
  liberty -> mitaka (trusty)
  mitaka -> newton (trusty)
  newton -> master (xenial)

Change-Id: I5c87e4b2c9315d6ac808e478a494a223fb875589

openstack-infra/project-config,Tesora/tesora-project-config,Tesora/tesora-project-config,openstack-infra/project-config