containerized-build: use dnf instead of yum
containerized-build: use dnf instead of yum

The Ceph base image moved to CentOS 8 which uses dnf. Use that instead
of yum.

Signed-off-by: Niels de Vos <7bda0c0ee7f47171cc808e9e60292cbc5d8140dd@redhat.com>

ceph/ceph-csi,ceph/ceph-csi,ceph/ceph-csi,ceph/ceph-csi