BugLink: https://bugs.launchpad.net/bugs/1828420

Upstream commit 7c0cca7c ("tty: ldisc:
add sysctl to prevent autoloading of ldiscs") backport applied as part
of upstream stable update to Linux 4.4.179 adds a new config option
LDISC_AUTOLOAD which default value is "y". Update the Ubuntu configs
accordingly.
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>