Dockerfile: virt-launcher: use collectd base image

Just switching to the backward-compatible libvirt-collectd
image, we get pod metrics reporting for free.

Signed-off-by: Francesco Romani <fromani@redhat.com>

cmd/virt-launcher/Dockerfile

@@ -16,7 +16,7 @@
 # Copyright 2017 Red Hat, Inc.
 #
 
-FROM kubevirt/libvirt:4.2.0
+FROM fromanirh/libvirt-collectd:4.2.0.11
 
 MAINTAINER "The KubeVirt Project" <kubevirt-dev@googlegroups.com>