Fedora 26 has been End-Of-Life for a long time already, is should not be
used anymore. Instead use the latest CentOS image that gets regular
updates. The Ceph base image used by Ceph-CSI is also based on CentOS,
so uses would be familiar with the available tools.
Also use "sleep infinity" instead of a weird 'tail -f /dev/null' hack.
Signed-off-by: Niels de Vos <ndevos@redhat.com>