Comment 8 for bug 842799

<seb128> http://www.freedesktop.org/wiki/Software/systemd/inhibit/
<seb128> "shutdown inhibits high-level system power-off and reboot requested by (unprivileged) users"
<seb128> that's part of logind
<seb128> (e.g it's already being used, not part of changing pid 1)
<seb128> like that page has an example of pseudo code
<seb128> "fd = Inhibit("shutdown:idle", "Package Manager", "Upgrade in progress...", "block");"
<seb128> that's basically what we want