Bug 1761090

Description of problem:

Installing updates at the end of the day via GNOME shutdown dialog is a nice way of not letting updates interrupt your workflow. Since around F29 (see additional info) this does not work reliably and needs to be triggered first via GNOME software which is annoying because it takes some time to refresh the update list and download the new updates for the checkbox to reappear.
The checkbox also appears if I get notified that updates are available. If I do not reboot/shutdown in the next five minutes after that, the checkbox is gone again.

Steps to Reproduce:
1. Open GNOME Software
2. Refresh update tab
3. Open GNOME shutdown dialog, checkbox to install updates on shutdown/reboot exists
4. Wait five minutes (look in journalctl for PackageKit quit)
5. Open GNOME shutdown dialog, checkbox is gone

Actual results:

Updates are not offered after a normal session (used longer than five minutes) on shutdown/reboot even though (security) updates exist.

Expected results:

Updates are always offered after a normal session (used longer than five minutes) on shutdown/reboot if (security) updates exist.

Additional info:

I found the following bug report which started the issue:
https://bugzilla.redhat.com/show_bug.cgi?id=1354074

This is the commit that disabled the PackageKit idle shutdown in 2014:
https://github.com/hughsie/PackageKit/commit/c6eb3555ec5b41e988c111d276764d55fb83bda3

This is the commit that enabled it again to “fix” the bug 1354074:
https://github.com/hughsie/PackageKit/commit/0c84d71509e851db20445c747529bd7d3724f081

This issue was already discussed once in a forum thread:
https://forums.fedoraforum.org/showthread.php?319895-Auto-updates-lost-after-upgrading-to-Fedora-29