Install libguestfs for nova-compute on Ubuntu

We were already installing this for n-cpu on rpm distros, but not
Ubuntu.  Install it so that nova-compute can use it for file injection,
which is the preferred method over nbd.

Set CONF.libvirt.inject_partition to -1.  This enables using libguestfs to
determine the proper partition to inject into.

Don't bother trying to load the nbd kernel module anymore.  It won't be used
since we know always expect libguestfs to be installed.

Change-Id: Ifa9d95bf759f1dad8685590a2df242d852dd2cb0

files/apts/n-cpu

@@ -1,8 +1,8 @@
 # Stuff for diablo volumes
-nbd-client
 lvm2
 open-iscsi
 open-iscsi-utils # Deprecated since quantal dist:precise
 genisoimage
 sysfsutils
 sg3-utils
+python-guestfs

lib/nova

@@ -240,8 +240,10 @@ function configure_nova() {
         sudo sysctl -w net.ipv4.ip_forward=1
 
         if [[ "$VIRT_DRIVER" = 'libvirt' ]]; then
-            # Attempt to load modules: network block device - used to manage qcow images
-            sudo modprobe nbd || true
+            # When libguestfs is available for file injection, enable using
+            # libguestfs to inspect the image and figure out the proper
+            # partition to inject into.
+            iniset $NOVA_CONF libvirt inject_partition '-1'
 
             # Check for kvm (hardware based virtualization).  If unable to initialize
             # kvm, we drop back to the slower emulation mode (qemu).  Note: many systems