centos-release-openstack-mitaka 1.3 is now available via the
delorean-mitaka-testing repo. We need to install this directly instead
of the 1.2 version as otherwise the subsequent 'yum update' tries to
install it and fails on the centos-release dependency which is
incompatible with the oraclelinux base.
Closes-Bug: 1576238
Change-Id: I51cb372424b27b32e95f9e81c5dddbe8e49a6131