Add base mock config for centos8
Add base mock config for centos8

We can use it for CI jobs instead of maintain it on de different ci
environments.

Change-Id: I3e8186d399f8a8c148fe8bb16292cef8e9d8c037

openstack-packages/delorean,openstack-packages/DLRN,openstack-packages/DLRN,openstack-packages/delorean