manifest: Add iptables-services
Currently, firewalld is the default for Fedora. However, both Docker
and Kubernetes do not yet know how to talk to it. Work is underway on
that, but in the meantime, iptables-services is an absolutely tiny
package, and the cost of carrying it forward is very small.
Bug: https://bugzilla.redhat.com/show_bug.cgi?id=1235843
Signed-off-by: Colin Walters <walters@verbum.org>