Change permissions on containers.conf

Although this doesn't cause any functional problems we get these errors during initial boot and the Podman API service (which we don't use) fails to start

Jul 20 17:30:17 master-0.ostest.test.metalkube.org systemd[4008]: Started Podman API Service.
Jul 20 17:30:17 master-0.ostest.test.metalkube.org podman[4019]: time="2022-07-20T17:30:17Z" level=error msg="reading system config \"/etc/containers/containers.conf\": decode configuration /etc/containers/containers.conf: open /etc/containers/containers.conf: permission denied"
Jul 20 17:30:17 master-0.ostest.test.metalkube.org podman[4018]: time="2022-07-20T17:30:17Z" level=error msg="reading system config \"/etc/containers/containers.conf\": decode configuration /etc/containers/containers.conf: open /etc/containers/containers.conf: permission denied"
Jul 20 17:30:17 master-0.ostest.test.metalkube.org podman[4020]: time="2022-07-20T17:30:17Z" level=error msg="reading system config \"/etc/containers/containers.conf\": decode configuration /etc/containers/containers.conf: open /etc/containers/containers.conf: permission denied"