dhclient exit hooks aren't guaranteed to run

ntp-systemd-netif.path contains the following:

[Install]
WantedBy=network-pre.target

However, network-pre.target is a passive systemd target. It is used only for ordering, and is not guaranteed to be pulled in unless something else calls for it explicitly.

On a host where nothing pulls in network-pre.target, the ntp-systemd-netif path monitoring never gets started, and so changes in
/run/systemd/netif/leases never trigger the dhclient exit hooks for ntp.

Instead, the systemd unit that starts the path monitoring should be configured with something like:

[Unit]
Wants=network-pre.target
Before=network-pre.target

[Install]
WantedBy=network.target