Disable Ubuntu motd Cruft

Canonical insist on advertising in their motd news as you log on. You get told you’re not part of ESM and click here to sign up - get rid of it all using the guidance from here:

https://askubuntu.com/a/1456185

Edit /usr/lib/update-notifier/apt_check.py

Change each of the following function definitions, so it returns without doing anything, by inserting a first line to return:

def _output_esm_package_count(outstream, service_type, esm_pkg_count):
    " output the number of packages upgrades related to esm service "
    return

def _output_esm_package_alert(
    outstream, service_type, disabled_pkg_count, is_esm=False
):
    " output the number of upgradable packages if esm service was enabled "
    return

def _output_esm_service_status(outstream, have_esm_service, service_type):
    return