Bug#862563: debian-live: Check for updates function don't work

[syl <syl@gresille.org>]

Package: debian-live
Severity: normal

Dear Maintainer,

After launch the command apt update, when you click in Settings > Details >
Check for updates, it say "Software is up to date". But when go to Synaptic,
they have a lot of upgrades to do.



-- System Information:
Debian Release: 9.0
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: amd64
 (x86_64)

Kernel: Linux 4.9.0-2-amd64 (SMP w/2 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)