Update ironbank.repo for ubi to be version generic

• Update our injected ironbank.repo file to utilize the new nexus groups which allow us to use the $releasever variable in the repo name and that allows us to inject a single ironbank.repo regardless of repo version.

Dependent on the completion of the bootstrap task to create the group repos.

[ubi]
name = Red Hat Universal Base Image (RPMs)
baseurl = http://nexus-repository-manager.nexus-repository-manager.svc.cluster.local:8081/repository/ubi-$releasever/
enabled = 1
gpgkey = file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release
gpgcheck = 1

• Once completed, we can remove the placeholder pipeline variable (DISTRO_REPO_DIR = '') in the UBI 7 repos that are currently in place as a band-aid.