Do not trigger install/upgrade for unreleased operating systems

After adding the has_install flag https://github.com/MariaDB/buildbot/blob/b602c0b06bb6f67f066ad9d83b4ec10af216126e/os_info.yaml#L62, builders are not created, but the builds are still scheduled. Do not trigger those builds if this is the case. One example of problematic builder is *-centos-stream8.