[ntp-admin] SMF service should explicitly depend on chrony setup

[karencfv]

Just a small change for correctness. We want to make sure ntp-admin depends on chrony having been configured, not just the NTP service being online. Also, the refresh behaviour on configuration being changed should be preserved.

I tagged a bunch of people who've worked on this service for a review. Wasn't exactly sure who to request a review from here.

[davepacheco]

Out of curiosity, why is this needed? I'm just thinking that if chrony is taking a while to come up, then with this change, we can't reach the ntp-admin service to even check the status. In an ideal world it would be nice if ntp-admin came up and operated as best it could (even if it's mostly returning errors) while chrony wasn't up yet.

[karencfv]

@davepacheco ntp-admin already indirectly depends on chrony-setup via the ntp service. Also, the chrony-setup service only generates and writes the chrony config file, it doesn't start chrony (ntp service does that). This means the existing behaviour is that if chrony takes a while to come up, ntp-admin would not come up.

This PR only makes the dependency explicit.

Going forward, I'm working on collecting more debug data from the NTP zone (#10407). To be able to answer questions like "Can I reach the upstream NTP server" I need to read chrony-setup's property group to get the necessary values. Preserving the refresh behaviour on configuration being changed means we avoid getting any false positives during a chrony-setup refresh.