nm-online times out, failing autopkgtests

The nm-online util does not return successfully as of 1.32.2-0ubuntu1 (currently in impish-proposed).

systemd VS network-manager autopkgtests (in LXD) fail, because the autopkgtest-virt-lxd runner tries to wait for "network ready" before it is reconnecting after a reboot. This happens by checking the 'systemctl start network-online.target' command, in turn executing the 'nm-online -s -q' util (via NetworkManager-wait-online.service), in addition to systemd-networkd-wait-online.service (which seems to be working OK).

nm-online does not return successfully anymore as of 1.32.2-0ubuntu1, but it times out. That is a regression compared to v1.30.

Reproducer:
$ lxc launch ubuntu-daily:impish test
$ lxc exec test bash
# apt install network-manager #(version 1.30.0-1ubuntu4)
# time systemctl start network-online.target

real 0m0.071s
user 0m0.021s
sys 0m0.023s
# time nm-online -s
Connecting............... 30s [started]

real 0m0.043s
user 0m0.027s
sys 0m0.006s
root@test:~# echo $?
0

Everything is OK up to here.

# vim /etc/apt/sources.list #(enable impish-proposed)
# apt update && apt install network-manager #(1.32.2-0ubuntu1)
# time nm-online -s
Connecting............... 0s [startup-pending]

real 0m30.019s
user 0m0.021s
sys 0m0.014s

# time systemctl start network-online.target

real 1m0.104s
user 0m0.013s
sys 0m0.023s
# journalctl -u NetworkManager | grep startup
Jul 15 09:05:06 test NetworkManager[1912]: <info> [1626339906.6507] manager: startup complete
root@test:~# NetworkManager -V
1.32.2
root@test:~# nm-online -s
Connecting............... 0s [startup-pending]
root@test:~# echo $?
1
root@test:~# nm-online
Connecting............... 0s [offline]
root@test:~# echo $?
1

The journal log contains the "startup completed" line, so 'nm-online -s' should return immediately. But as we can see, nm-online fails (after a timeout) and thus blocks network-online.target, failing the systemd autopkgtests (in LXD).