[JIRA] (OVIRT-2138) Revert "open external repos for master until centos 7.5 calms down"

Revert "open external repos for master until centos 7.5 calms down" ------------------------------------------------------------------- Key: OVIRT-2138 URL: https://ovirt-jira.atlassian.net/browse/OVIRT-2138 Project: oVirt - virtualization made easy Issue Type: Task Reporter: Dafna Ron Assignee: infra I created the ticket but need to make sure it passes CI before merging: https://gerrit.ovirt.org/#/c/91936/