[rdo-list] Remove periodic upgrade CI jobs from ci.centos

[mathieu bultel]

Hi,

As discussed yesterday with Emilien, Sofer and Wes, we decided to remove
the RDO upgrade ci jobs (periodic) from ci.centos.org since the workflow
of the current tripleo upgrade is too big and slow. The duration of the
jobs in the ci.centos infra take too much time, the jobs is hitting
timeout or is running out of memory.

The goal would be to put the effort on the upstream upgrade jobs with
the new workflow: composable upgrade for Newton to Ocata. The workflow
is light, and the ability of the use of the multinode save us from the
timeout.

We will implement the same workflow in tripleo-quickstart to be able to
re-build new upgrade jobs on centos CI.

Here is the discussion and the information:

https://etherpad.openstack.org/p/tripleo-upgrade-jobs

The review which drop the Upgrade jobs:

https://review.rdoproject.org/r/#/c/4114/

The first start of the composable upgrade with tripleo-quickstart:

https://review.openstack.org/410826