Adjust base_centos_yum_repo_packages for master
Adjust base_centos_yum_repo_packages for master

Kolla upstream is adding centos-release-openstack-train release rpm in
master branch after [1]. In tripleo builds this means it's configuring
both RDO Trunk master (delorean) repos and CloudSIG train repo. Mixing
both sets of repos can lead to undesired results so I'm removing
centos-release-openstack-train repo from config and letting
tripleo-repos configure as needed.

Also, I'm removing leftovers from old Ceph releases configuration.
Currently kolla is installing centos-release-ceph-nautilus so, tripleo
does not need to overrides it.

[1] https://review.opendev.org/#/c/689706

Change-Id: Ia551a7d2351bb91cc45e9c2d12f4afb4f6368bb7

openstack/tripleo-common,openstack/tripleo-common