Add qemu-img also in nova-libvirt image

This is noop on CentOS (it was installed as a dep already - better
be explicit) but installs qemu-img (and other qemu utils) on
Debian and Ubuntu.

qemu-img may be used by libvirtd to create non-raw images as it
happens, e.g., when Kolla's libvirtd is used by tenks.

Change-Id: Ib79b8486f4d5064e4f249201d28cf5d6541c69ef

docker/nova/nova-libvirt/Dockerfile.j2

@@ -22,6 +22,7 @@ LABEL maintainer="{{ maintainer }}" name="{{ image_name }}" build-date="{{ build
         'libvirt-daemon-config-nwfilter',
         'libvirt-daemon-driver-nwfilter',
         'openvswitch',
+        'qemu-img',
         'qemu-kvm',
         'trousers'
     ] %}
@@ -49,6 +50,7 @@ LABEL maintainer="{{ maintainer }}" name="{{ image_name }}" build-date="{{ build
         'python3-rbd',
         'qemu-block-extra',
         'qemu-system',
+        'qemu-utils',
         'trousers'
     ] %}