Bug#275710: xserver-xfree86: preinst script fails when upgrading from 4.0.2-7 to 4.3.0.dfsg.1-8

[Florian Laws]

Commenting out

    db_unregister xserver-xfree86/manage_config_with_debconf
    db_unregister xserver-xfree86/move_existing_nondebconf_config

at the bottom of the preinst script seemed to work around the problem.

At first, the installation aborted with a segfault in the postinst,
but another --configure completed, and the X server is now running.