Description of problem:

Old workaround for https://bugzilla.redhat.com/show_bug.cgi?id=1378974 still exists, preventing systemd-udev-trigger.service to be restarted.

This actually has a side-consequences for systemd-networkd, because whenever you update a .link file, you need to restart systemd-udev-trigger to get changes applied to the link during runtime.

At the moment, this results in a following error:
# systemctl restart systemd-udev-trigger
Failed to restart systemd-udev-trigger.service: Operation refused, unit systemd-udev-trigger.service may be requested by dependency only (it is configured to refuse manual start/stop).
See system logs and 'systemctl status systemd-udev-trigger.service' for details.
#

This happens because an override is packaged to workaround a bug above:
# cat /usr/lib/systemd/system/systemd-udev-trigger.service.d/systemd-udev-trigger-no-reload.conf 
[Unit]
# https://bugzilla.redhat.com/show_bug.cgi?id=1378974#c17
RefuseManualStop=true
#

Version-Release number of selected component (if applicable):

systemd-257-16

Steps to Reproduce:
1. Edit some .link file for systemd-networkd. Ie, by adding an `Alias`: https://www.freedesktop.org/software/systemd/man/latest/systemd.link.html#Alias=
2. Reload the daemon
3. Restart systemd-udev-trigger.service

Actual results:

Restart fails to execute

Expected results:

Restart happens and interface gets alias applied without system reboot.

Additional info:

It seems that the initial bug linked above was resolved on it's own and this override is not needed anymore, as %postun should not be present on any supported system now.