[ajax] fix the fix introduced in 3.9.1 to avoid duplicated loads: it cause some other errors since the browser may load the script *after* the server-response event is emited, causing pb if the script interact with this event

#!/bin/sh -e
if [ "$1" = "purge" ] ; then
        update-rc.d cubicweb remove >/dev/null
fi
 
#DEBHELPER#
 
exit 0