I'm running ubuntu 13.04 on my Thinkpad T430. Whenever I shutdown, a terminal message which seems (at least, in part) to be related to Virtualbox, but I'm not sure:

Is there a way to hide these messages during shutdown? They do not appear during boot.
What I've tried:
I edited my /etc/init/rc.conf file and commented out console output like this:
# rc - System V runlevel compatibility
#
# This task runs the old System V-style rc script when changing between
# runlevels.
description "System V runlevel compatibility"
author "Scott James Remnant <scott@netsplit.com>"
emits deconfiguring-networking
emits unmounted-remote-filesystems
start on runlevel [0123456]
stop on runlevel [!$RUNLEVEL]
export RUNLEVEL
export PREVLEVEL
#console output
env INIT_VERBOSE
task
exec /etc/init.d/rc $RUNLEVEL
This resulted in a shorter but still present terminal message:

I also tried running a shutdown from terminal simply running sudo init 0 but the acpid: exiting message persists.