Libreoffice doesn't terminate all processes after running with --headless

I am trying to convert DRAW diagrams to EPS using the --convert-to option in headless mode.

This works as expected when running the command directly on the command line in a shell. Now, In my case I run it on a cluster using GridEgine (out of my control), so the conversion job is submitted to a farm. Everything runs fine but the problems is that eventhough the --headless option is specified then libreoffice starts two processes (I guess due to the fact it needs Gnome for something):

913  0.0  0.0  16088   632 ?        S    10:19   0:00 dbus-launch --autolaunch=ce05c690d97e464586264e864c49b504 --binary-syntax --close-stderr
914  0.0  0.0  28560   732 ?        Ss   10:19   0:00 /bin/dbus-daemon --fork --print-pid 5 --print-address 7 --session

The problem is then that the job cannot exit since there are processes still running which means that it hangs. I have handled this by using pkill to kill these processes but I do not think it is a nice solution.

Any other ways to handle this?