unattended-upgrade hangs on shutdown when network is required for updates

There are two modes of running u-u chosen by setting Unattended-Upgrade::InstallOnShutdown to "false" (default) or "true".

When InstallOnShutdown is "false" apt's apt-daily-upgrade.service runs u-u thus this service needs to ensure that network is still up, to not break similar packages.

Note that while vast majority of packages do not need network connection during installation a small fraction of them do perform downloads thus apt's service should try to keep the network up.

When InstallOnShutdown is "true" unattended-upgrades.service is responsible for keeping the network connection up and I believe versions starting with 0.93.1+nmu1 are fixed.

grr. So we actually need to add an After=network.target there for shutdown. For start up, we actually also need to do the whole network-online dance, meaning

<= 1.4.y:
 After=network-online.target Wants=network-online.target

>= 1.5.y:

 After=network.target network-online.target systemd-networkd.service NetworkManager.service connman.service
 ExecStartPre=-/usr/lib/apt/apt-helper wait-online

(basically, just copy that stuff from apt-daily.service)

Installer packages are fun!

I guess I'll really have to do 1.6~alpha1 finally this week, so I'll put it in there, and after we have verified and migrated the old SRUs, we can do SRUs for stable releases as well (1.2.26, 1.4.9, 1.5.1).

This really is the APT problem with the most fixups ever :D :(

This bug was fixed in the package apt - 1.7.0~alpha1

---------------
apt (1.7.0~alpha1) experimental; urgency=medium

  [ Julian Andres Klode ]
  * CMake: Fix builds without zstd
  * apt.conf.autoremove: Catch some new Ubuntu module packages
  * Fix build with new gtest (Closes: #897149)
  * tests: Do not expect requested-by if sudo was invoked by root
  * Run tests on GitLab CI
  * Handle a missed case of timed out ip addresses (LP: #1766542)
  * Lower default timeout from 120s to 30s
  * apt-key: Pass all instead of gpg-agent to gpgconf --kill (LP: #1773992)
  * Fix lock counting in debSystem
  * CI: Export DEBIAN_FRONTEND=noninteractive in all CI environments
  * Ensure that we are online in apt-daily-upgrade.service (LP: #1723761)
  * gitlab-ci: chmod 755 /root

  [ David Kalnischkies ]
  * move special READMEs into doc/ and format as md
  * Add boilerplate plural form to po/apt-all.pot
  * don't try SRV requests based on IP addresses
  * use 127.0.0.1 instead of localhost as default Tor proxy
  * Extend apt build-dep pkg/release to switch dep as needed
  * Support release selector for volatile files as well
  * Start pkg records for deb files with dpkg output
  * Deprectate buggy/incorrect Rls/PkgFile::IsOk methods
  * Support --with-source in show & search commands
  * Support local files as arguments in show command (Closes: 883206)
  * Drop alternative URIs we got a hash-based fail from
  * Handle by-hash URI construction more centrally
  * Don't force the same mirror for by-hash URIs
  * Reword error for timed out read/write on SOCKS proxy (Closes: #898886)
  * Don't show acquire warning for "hidden" components (Closes: #879591)
  * Use a steady clock source for progress reporting
  * Use steady clock source for bandwidth limitation

  [ Guillem Jover ]
  * Remove obsolete RCS keywords
  * Normalize authors through a mailmap file
  * po: Fill Project-Id-Version with correct project id and version
  * po: Fix translated string not matching format string arguments
  * po: Fix Language field to match actual locale
  * po: Remove spurious text in Plural-Forms field
  * po: Add missing Plural-Forms fields

  [ Filipe Brandenburger ]
  * Update .gitignore
  * Increase debug verbosity in `apt-get autoremove`
  * Extend test-apt-get-autoremove to check debug output

  [ annadane ]
  * Add verb 'be' to NEWS entry for 1.5~beta1 (Closes: 892792)

  [ Алексей Шилин ]
  * Russian program translation update (Closes: 898797)

  [ Frans Spiesschaert ]
  * Dutch program translation update (Closes: #900589)
  * Dutch manpage translation update (Closes: #900602)

 -- Julian Andres Klode <email address hidden> Mon, 25 Jun 2018 17:12:30 +0200