Adding vfio to cgroup_device_acl during libvirt configuration

vfio should be added to cgroups on some of the Distributions like
Ubuntu 16-04

Change-Id: I7239858b6307e37bf1237b92d69a0520ab5ad304
diff --git a/lib/nova_plugins/functions-libvirt b/lib/nova_plugins/functions-libvirt
index cc013c3..6b7c7c2 100644
--- a/lib/nova_plugins/functions-libvirt
+++ b/lib/nova_plugins/functions-libvirt
@@ -65,6 +65,7 @@
     "/dev/random", "/dev/urandom",
     "/dev/ptmx", "/dev/kvm", "/dev/kqemu",
     "/dev/rtc", "/dev/hpet","/dev/net/tun",
+    "/dev/vfio/vfio",
 ]
 EOF
     fi