Comment 5 for bug 1244736

Using:
grep -q "^use-ssh-agent$" /etc/X11/Xsession.options || { stop; exit 0; }
To detect whether or not to launch the ssh agent doesn't seem to make sense to me, since if "use-ssh-agent" is true then ssh-agent will be setup by /etc/X11/Xsession.d/90x11-common_ssh-agent (and later launched), so there doesn't seem to be a need for an upstart script here.