Comment 17 for bug 1173013

Looking at update-gconf-defaults we see:

if 'DPKG_RUNNING_VERSION' in os.environ and options.signal:
    # This is what happens when we are called in an obsolete postinst/prerm script
    # Do nothing, it will be done in the trigger
    sys.exit(0)

So when the postinst script calls update-gconf-defaults it just exits.