Bug#989317: systemd kill background processes after user logs out (#825394 regression)

[Matt Corallo]

Package: systemd
Version: 247.3-5

After upgrading to bullseye on a test machine, spawning an lxc container with systemd-run[1] still kills the lxc 
container after the spawning shell is closed (and the user logs out). No only does the lxc container eventually get 
killed, but systemd refuses any further login for the user while it waits for the lxc container to die (something like 
maybe 30 seconds for a simple lxc container running an sshd service), making it appear the system has hung.

This doesn't appear to be resolved by the options suggested in the man page for systemd-run like `loginctl 
enable-linger` or `KillUserProcesses=no` (which appears to still be the default).

Matt

[1] eg systemd-run --user -p "Delegate=yes" --unit=fuzzer -- lxc-start --name fuzzer -- /usr/sbin/sshd -D