[pkg] Stop using /etc/bash_completion.d cubicweb-ctl shipped an empty /etc/bash_completion.d as a leftover of shipping a bash completion script. As pointed by Lintian, this directory is not obsolete, so let's get rid of it for good.

#!/bin/sh -e

if [ "$1" = "purge" ] ; then
        rm -rf /etc/cubicweb.d/
        rm -rf /var/log/cubicweb/
        rm -rf /var/lib/cubicweb/
fi

#DEBHELPER#
 
exit 0