[transaction] initialize hook control attribute in Transaction
There is no reason to not initialize them in __init__ time. this simplify the
transaction code.
#! /bin/sh -ecase "$1" in remove) if [ -x "/etc/init.d/cubicweb-ctl" ]; then invoke-rc.d cubicweb-ctl stop || true fi ;;esac#DEBHELPER#exit 0