Remove TODO in libvirt script

This is no longer required when Kolla-Ansible is patched.

Note this is *not* safe to backport as it requires the user to
have Kolla-Ansible patched, i.e. would normally break most.

Change-Id: Ic5b9a58d212711a4d6c13822548c92013a6bae50
Related-Bug: #1681461
Depends-On: https://review.opendev.org/735441

docker/nova/nova-libvirt/extend_start.sh

@@ -1,13 +1,5 @@
 #!/bin/bash
 
-# TODO(SamYaple): Tweak libvirt.conf rather than change permissions.
-# Fix permissions for libvirt
-# Do not remove unless CentOS has been validated
-if [[ -c /dev/kvm ]]; then
-    chmod 660 /dev/kvm
-    chown root:qemu /dev/kvm
-fi
-
 # Mount xenfs for libxl to work
 if [[ $(lsmod | grep xenfs) ]]; then
     mount -t xenfs xenfs /proc/xen