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

Upstream commit c7084edc ("tty: mark
Siemens R3964 line discipline as BROKEN") backport applied as part of
upstream stable update to Linux 4.4.179 disables the n_r3964 module.
Update the Ubuntu configs to remove the broken module.
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>