Install vhost-net module

[Ian Wells]

libvirt will use the vhost-net kernel module, if it's in the kernel at the time you start a VM. This significantly improves network performance for VMs. There's no good reason not to turn it on, and it should be added to the default COI setup.

(Needs to be probed and also put in /etc/modules)

[Ian Wells (ijw-ubuntu)]

Trivial and somewhat naive way to do it:

define load_module() {
    exec {
        "addmod_$title":
            command => "/bin/echo '$title' >>/etc/modules",
            unless => "/bin/egrep '^$title' /etc/modules",
            notify => Exec["modprobe_$title"];
    }

    exec {
        "modprobe_$title":
            command => "/sbin/modprobe ${name} || :",
            refreshonly => true;
    }
}

... then call from node os_base (in Grizzly).
Be nicer if it had present/absent and also if it used augeas, but I couldn't find a lens that works with the Ubuntu-shipping version.