Remove cgroup natty or less block

Given that Natty and other releases that don't use cgroups have been out
of support in Ubuntu for years now, it's high time we removed the
special case code block that sets up the cgroup mount.

Change-Id: I5403a4b1b64a95236b4dfcb66c35c594a3460cca

lib/nova

@@ -303,17 +303,6 @@ function configure_nova {
             # to simulate multiple systems.
             if [[ "$LIBVIRT_TYPE" == "lxc" ]]; then
                 if is_ubuntu; then
-                    if [[ ! "$DISTRO" > natty ]]; then
-                        local cgline="none /cgroup cgroup cpuacct,memory,devices,cpu,freezer,blkio 0 0"
-                        sudo mkdir -p /cgroup
-                        if ! grep -q cgroup /etc/fstab; then
-                            echo "$cgline" | sudo tee -a /etc/fstab
-                        fi
-                        if ! mount -n | grep -q cgroup; then
-                            sudo mount /cgroup
-                        fi
-                    fi
-
                     # enable nbd for lxc unless you're using an lvm backend
                     # otherwise you can't boot instances
                     if [[ "$NOVA_BACKEND" != "LVM" ]]; then