Code review comment for lp:~mterry/telephony-service/start-on

I realized that maybe the goal of "started unity8" was to only run in Touch. If so, then maybe do the same thing that indicator-network did:

pre-start script
        # NOTE: Only used on Unity8 today, not 7
        if [ "x$DESKTOP_SESSION" != "xubuntu-touch" ] ; then
                stop; exit 0
        fi
end script